Python_cs1002.pdf

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Introduction to Python

Section I Prof. Kalpesh Joshi VIT, Pune

Identifiers

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An identifier is a word used to name things  One of the thing an identifiers can name is Variable, therefore variable name is an example of an identifier.  Identifiers have following forms  Identifiers must contain at least one character  The first character must be an alphabetic letter, underscore .  Remaining can be alphabet, underscore or digit.  No other characters are permitted in Identifiers .  Identify the valid Identifier x,x2,total,sub-total,FLAG,4all,Class 

Reserved keywords

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



Python reserves some words for special use called reserved keywords. None of reserved keywords should be used by Identifiers, if so it issues error. example: Class = 15 In above example it will shows syntax error, since class is Reserve keyword.

Variables

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





In algebra, variables defines number same python represents values other than numbers. ex: x = 10 print(x) Where x is variable, = is assignment operator, 10 is value or integer so it prints variable ‘x’. Variable names may be any contiguous sequence of letters,numbers,underscore. We can not use reserved word as variable

Comments in python and Indentation in Python

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•Anything after #symbol is comment. ex: print “Hello world” avg=sum/num #computes the average of values •Comments are not part of command which can be used by anyone reading code. •Indentation : A code block (body of a function, loop etc.) starts with indentation and ends with the first unindented line. The amount of indentation is up to you, but it must be consistent throughout that block. •Generally four whitespaces are used for indentation and is preferred over tabs.

Input, Output operation in in python

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Python provides numerous built-in functions that are readily available to us at the Python prompt. Some of the functions like input() and print() are widely used for standard input and output operations respectively. We use the print() function to output data to the standard output device (screen).

How to read and write in Python

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Every program is eventually a data processor, so we should know how to input and output data within it. There exists a function, print(), to output data from any Python program. To use it, pass a comma separated list of arguments that you want to print to the print() function. Let's see an example. Press "run" and then "next" to see how the program is being executed line by line: print(5 + 10) # Result : 15 print(3 * 7, (17 - 2) * 8) # Result : 21 120 print(2 ** 16) # two stars are used for exponentiation (2 to the power of 16) # Result : 65536 print(37 / 3) # single forward slash is a division (12.3333) print(37 // 3) # double forward slash is an integer division # it returns only the quotient of the division (i.e. no remainder) print(37 % 3) # percent sign is a modulus operator # it gives the remainder of the left value divided by the right value ( Result : 1)

How to read and write in Python

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To input data into a program, we use input(). This function reads a single line of text, as a String. Here's a program that reads the user's name and greets them:

print('What is your name?') name = input() # read a single line and store it in the variable "name“ print('Hi ' + name + '!')

Sum of numbers and strings

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Let's try to write a program that inputs two numbers and prints their sum. We read the two numbers and store them in the variables a and b using the assignment operator =. On the left side of an assignment operator we put the name of the variable. The name could be a string of latin characters (A-Z, az, 0-9, _) but must start with a letter in the range A-Z or a-z. On the right side of an assignment operator we put any expression that Python can evaluate. The name starts pointing to the result of the evaluation. Read this example, run it and look at the output: a = input() b = input() s=a+b print (s) Note: After running the example we can see that it prints 57. As we were taught in school, 5 + 7 gives 12. So, the program is wrong, and it's important to understand why. The thing is, in the third line s = a + b Python has "summed" two strings, rather than two numbers. The sum of two strings in Python works as follows: they are just glued one after another. It's also sometimes called "string concatenation".

Sum of numbers and strings

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

Do you see in the variable inspector, on the right hand side, that the values bound to variables a and b are wrapped in quotes? That means that the values there are string, not numbers. Strings and numbers are represented in Python differently.

Sum of numbers and strings

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All the values in Python are called "objects". Every object has a certain type. The number 2 corresponds to an object "number 2" of type "int" (i.e., an integer number). The string 'hello' corresponds to an object "string 'hello'" of type "str". Every floating-point number is represented as an object of type "float". The type of an object specifies what kind of operations may be applied to it. For instance, if the two variables "first" and "second" are pointing to the objects of type int, Python can multiply them. However, if they are pointing to the objects of type str, Python can't do that: first = 5 second = 7 print(first * second)



# you can use single or double quotes to define a string first = ‘5’ second = ‘’7’’ print(first * second)

Sum of numbers and strings

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To cast (convert) the string of digits into an integer number, we can use the function int(). For example, int('23')gives an int object with value 23. Given the information above, we can now fix the incorrect output and output the sum of the two numbers correctly: a = int(input()) b = int(input()) s=a+b print(s) Result : if a= 5 and b=7 then output is 12.

Docstrings

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

 



Python also has extended documentation capability, called docstrings. Docstrings can be one line, or multiline. Python uses triple quotes at the beginning and end of the docstring: Example Docstrings are also comments: """This is a multiline docstring.""" print("Hello, World!")

Python Variables

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Creating Variables : Unlike other programming languages, Python has no command for declaring a variable. A variable is created the moment you first assign a value to it. Example: x=5 y = "John" print(x) print(y) Variables do not need to be declared with any particular type and can even change type after they have been set.

Python Variables - Example

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x = 4 # x is of type int x = "Sally" # x is now of type str print(x)

Variable Names

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A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for Python variables: A variable name must start with a letter or the underscore character A variable name cannot start with a number A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) Variable names are case-sensitive (age, Age and AGE are three different variables)

Note : Remember that variables are case-sensitive

Output Variables

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The Python print statement is often used to output variables.

To combine both text and a variable, Python uses the + character: Example : x = "awesome" print("Python is " + x) You can also use the + character to add a variable to another variable: Example : x = "Python is " y = "awesome" z= x+y print(z)

Output Variables

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For numbers, the + character works as a mathematical operator: Example : x=5 y = 10 print(x + y) Note : If you try to combine a string and a number, Python will give you an error: Example: x=5 y = "John" print(x + y)

Basic data types in python

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Every value in Python has a data type. Since everything is an object in Python programming, data types are actually classes and variables are instance (object) of these classes. There are various data types in Python. Some of the important types are listed below. 1. Integer 2. Floating point number 3. Complex number 4. String 5. Boolean – True – Non zero false - Zero Note: We can use the type() function to know which class a variable or a value belongs to

Python Numbers

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Python Numbers : There are three numeric types in Python: 1.int 2. float 3.Complex Variables of numeric types are created when you assign a value to them: Example : x = 1 # int y = 2.8 # float z = 1j # complex To verify the type of any object in Python, use the type() function: Example : print(type(x)) print(type(y)) print(type(z))

Int

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Int, or integer, is a whole number, positive or negative, without decimals, of unlimited length. Example : Integers: x=1 y = 35656222554887711 z = -3255522 print(type(x)) print(type(y)) print(type(z))

Float

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Float, or "floating point number" is a number, positive or negative, containing one or more decimals. Example Floats: x = 1.10 y = 1.0 z = -35.59 print(type(x)) print(type(y)) print(type(z))

Float

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Note: Float can also be scientific numbers with an "e" to indicate the power of 10. Example Floats: x = 35e3 y = 12E4 z = -87.7e100 print(type(x)) print(type(y)) print(type(z))

Complex

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Complex numbers are written with a "j" as the imaginary part: Example: Complex: x = 3+5j y = 5j z = -5j print(type(x)) print(type(y)) print(type(z))

Python Operators

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Operators are the constructs which can manipulate the value of operands. Consider the expression 4 + 5 = 9. Here, 4 and 5 are called operands and + is called operator. Operators are used to perform operations on variables and values. Python divides the operators in the following groups: Arithmetic operators Assignment operators Comparison operators Logical operators Identity operators Membership operators Bitwise operators

+ Addition

Python Arithmetic Operators

Adds values on either side of the operator.

a + b = 30

- Subtraction Subtracts right hand operand from left hand a – b = -10 VI  Arithmetic operators are used with numeric values to operand.

perform common mathematical operations:

* Multiplication Multiplies values on either side of the operator

a * b = 200

/ Division

Divides left hand operand by right hand operand

b/a=2

% Modulus

Divides left hand operand by right hand operand and returns remainder

b%a=0

** Exponent

//

Performs exponential (power) calculation on operators

a**b =10 to the power 20

Floor Division - The division of operands where 9//2 = 4 and the result is the quotient in which the digits after 9.0//2.0 = the decimal point are removed. But if one of the 4.0, -11//3 operands is negative, the result is floored, i.e., = -4, rounded away from zero (towards negative 11.0//3 = infinity) − 4.0

Python Arithmetic Operators

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Arithmetic operators are used with numeric values to perform common mathematical operations:

Operator

Name

Example

+

Addition

x+y

-

Subtraction

x-y

*

Multiplication

x*y

/

Division

x/y

%

Modulus

x%y

**

Exponentiation

x ** y

//

Floor division

x // y

Python Assignment Operators

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Assignment operators are used to assign values to variables: Operator

Example

Same As

=

x=5

x=5

+=

x+=3

x=x+3

-=

x-=3

x=x-3

*=

x *= 3

x=x*3

/=

x /= 3

x=x/3

%=

x %= 3

x=x%3

//=

x //= 3

x = x // 3

**=

x **= 3

x = x ** 3

Example - Python Assignment Operators

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1.

x=5 x+=3 print(x) { 8} 2. x = 5 x-=3 print(x) {2} 3. x = 5 x% =3 print(x) {2} 4. x = 5 x//=3 print(x) {1} 5. x = 5 x **= 3 print(x) {125}

Operator

Example

Same As

=

x=5

x=5

+=

x+=3

x=x+3

-=

x-=3

x=x-3

*=

x *= 3

x=x*3

/=

x /= 3

x=x/3

%=

x %= 3

x=x%3

//=

x //= 3

x = x // 3

**=

x **= 3

x = x ** 3

Python Comparison Operators

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These operators compare the values on either sides of them and decide the relation among them. They are also called Relational operators.

Operator

Name

Example

==

Equal

x == y

!=

Not equal

x != y

>

Greater than

x>y

<

Less than

x
>=

Greater than or equal x >= y to

<=

Less than or equal to

x <= y

Example - Python Comparison Operators

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1. x = 5 y=3 print(x == y) Operator # returns False because 5 is not equal to 3 = 2. x = 5 += y=3 print(x != y) -= # returns True because 5 is not equal to 3 *= 3. x = 5 /= y=3 print(x > y) %= # returns True because 5 is greater than 3 //= 4. x = 5 **= y=3 print(x < y) # returns False because 5 is not less than 3 5. x = 5 y=3 print(x > = y) # returns True because five is greater, or equal, to 3

Example Same As

x=5

x=5

x+=3

x=x+3

x-=3

x=x-3

x *= 3

x=x*3

x /= 3

x=x/3

x %= 3

x=x%3

x //= 3

x = x // 3

x **= 3

x = x ** 3

Python Logical Operators Logical operators are used to combine conditional statements:

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Operator

Description

Example

and

Returns True if both statements are true

x < 5 and x < 10

or

Returns True if one of x < 5 or x < 4 the statements is true

not

Reverse the result, returns False if the result is true

Example of AND x=5 print(x > 3 and x < 10) # returns True because 5 is greater than 3 AND 5 is less than 10 Example of NOT x=5 print(not(x > 3 and x < 10)) # returns False because not is used to reverse the result

not(x < 5 and x < 10) Example of OR x=5 print(x > 3 or x < 4) # returns True because one of the conditions are true (5 is greater than 3, but 5 is not less than 4)

Python Membership Operators

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Membership operators are used to test if a sequence is presented in an object: Operator

Description

Example

Meaning

in

Returns True if a sequence with the specified value is present in the object

x in y

True if the operands are identical ( refer to the same object)

not in

Returns True if a sequence with the specified value is not present in the object

x not in y

True if the operands are not identical ( do not refer to the same object)

Example of in operator : x = ["apple", "banana"] print("banana" in x) # returns True because a sequence with the value "banana" is in the list

Example of not in operator x = ["apple", "banana"] print("pineapple" not in x) # returns True because a sequence with the value "pineapple" is not in the list

Conclusion

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Logical operator are same for c and python. For example : x = 5 > 2 means condition true that means x = 2 && : logical and ∣∣ : logical or ! : not ( false becomes true and true becomes false) Bitwise operator:

Operator

meaning

&

Bitwise AND

∣

Bitwise OR

~

Bitwise NOT

^

Bitwise XOR

>>

Bitwise right shift

<<

Bitwise left shift

Python Operators Precedence

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The following table lists all operators from highest precedence to lowest. Sr.No.

Operator & Description

1

** Exponentiation (raise to the power)

2

~+Complement, unary plus and minus (method names for the last two are +@ and -@)

3

* / % // Multiply, divide, modulo and floor division

4

+Addition and subtraction

5

>> << Right and left bitwise shift

6

& Bitwise 'AND'

7

^| Bitwise exclusive `OR' and regular `OR'

8

<= < > >= Comparison operators

9

<> == != Equality operators

10

= %= /= //= -= += *= **= Assignment operators

11

is is not Identity operators

12

in not in Membership operators

13

not or and Logical operators

Control flow statement

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Decision making : 1. if statement 2. if … else 3. if … else if …else 4. Nested if statement

1.

if statement: This statements control the flow of execution. It is basically used for testing condition. The general form of if statement looks like this: if ( this condition is true ) execute this statement An "if statement" is written by using the if keyword. Example If statement: a = 33 b = 200 if b > a: ( colon : represents indentation ) print("b is greater than a")

Indentation

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python relies on indentation, using whitespace, to define scope in the code. Other programming languages often use curly-brackets for this purpose.

Example : If statement, without indentation (will raise an error): a = 33 b = 200 if b > a: print("b is greater than a") # you will get an error

if…else

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if else conditional statement in Python has the following syntax: if condition: true-block several instructions that are executed if the condition evaluates to True else: false-block several instructions that are executed if the condition evaluates to False Syntax : if (condition/test expression): statement1 statement 2 True block else:

statement 1 statement 2 statement x

false block

if…else

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Prog: Given number is positive and Negative n = int( input (“Enter n value ”)) if ( n > 0) : print(“Positive”) else: print(“Negative)

Nested if

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when a programmer writes one if statement inside another if statement then it is called as Nested if statement

There may be a situation when you want to check for another condition after a condition resolves to true. In such a situation, you can use the nested if construct. In a nested if construct, you can have an if...elif...else construct inside another if...elif...else construct.

Nested if

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Syntax: if ( condition1/test expression): if (condition2/test expression): statement1 inner statement n true else: statement2 inner statement n false else: statement 3 statement n

True Block

Note: In above syntax , if condition1 and condition 2 are correct then statement 1 will execute . If the condition1 is correct and condition 2 is incorrect then statement 2 will execute . If the both condition1 and condition 2 are incorrect then statement 3 is execute.

Example - Nested if

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Write a programme to read three numbers from a user and check if the first number is greater or less than the other two numbers num1= int(input(“Enter the number:”)) num2= int(input(“Enter the number:”)) num3= int(input(“Enter the number:”)) if (num1 > num2): if ( num2 > num3): print(num1,”is greater than”, num2,”and”, num3) else: print(num1,”is less than”, num2,”and”,num3) Print(“End of Nested if “) Output: Enter the number:12 Enter the number: 34 Enter the number: 56 12 is less than 34 and 56 End of Nested if

Example : Nested if

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Prog: find largest among 3 number a = int( input (“Enter value of a”)) b = int( input (“Enter value of b”)) c = int( input (“Enter value of c”)) if ( a > b) : if ( a > c) # if this condition fails then it executes print(“a is large”) else part ( c is large ) else: print(“c is large”) elif ( b > c) : # if ( a > b) fails then control will enter print(“ b is large”) at elif . To check one more condition else: use elif (elseif) print( “ c is large”)

The elif Statement

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The elif statement allows you to check multiple expressions for TRUE and execute a block of code as soon as one of the conditions evaluates to TRUE. Similar to the else, the elif statement is optional. However, unlike else, for which there can be at most one statement, there can be an arbitrary number of elif statements following an if.

Syntax: if expression1: statement(s) elif expression2: statement(s) elif expression3: statement(s) else: statement(s)

In this kind of statements, the expression are checked from top to bottom. When true condition is found, the associate statement are executed and rest statement are skipped. If none of condition are found true then else statements are executed. if all other condition are false and if the final else statement is not present then no action takes place.

Example - elif Statements

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var = 100 If var == 200: print ("1 - Got a true expression value") print (var) elif var == 150: print ("2 - Got a true expression value") print (var) elif var == 100: print ("3 - Got a true expression value") print (var) else: print ("4 - Got a false expression value") print (var) print ("Good bye!") Output 3 - Got a true expression value 100 Good bye!

if...elif...else construct

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var = 100 if var < 200: print ("Expression value is less than 200") if var == 150: print ("Which is 150") elif var == 100: print ("Which is 100") elif var == 50: print ("Which is 50") elif var < 50: print ("Expression value is less than 50") else: print ("Could not find true expression") print ("Good bye!") output Expression value is less than 200 Which is 100 Good bye!

Nested condition

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x = int(input( )) y = int(input( )) if x > 0: if y > 0: # x is greater than 0, y is greater than 0 print("Quadrant I") else: # x is greater than 0, y is less or equal than 0 print("Quadrant IV") else: if y > 0: # x is less or equal than 0, y is greater than 0 print("Quadrant II") else: # x is less or equal than 0, y is less or equal than 0 print("Quadrant III")

Input 2 -3

Output Quadrant IV

if-elif-else

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For the given integer X print 1 if it's positive, -1 if it's negative, or 0 if it's equal to zero. Try to use the cascade if-elif-else for it.

x = int(input( )) if x > 0: print(1) elif x == 0: print(0) else: print(-1)

Examples

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Write a python program where a student can get a grade based on marks that he has scored in any subject. Suppose that marks 90 and above are A’s, marks in the 80s are B’s, 70s are C’s, 60s are D’s, and anything below 60 is an F. Use ‘if’ statement.

Code: grade = int (input('Enter your score: ')) if grade>=90: print('A') if grade>=80 and grade<90: print('B') if grade>=70 and grade<80: print('C') if grade>=60 and grade<70: print('D') if grade<60: print('F')

Examples

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Write a program that asks the user to enter a length in centimeters. If the user enters a negative length, the program should tell the user that the entry is invalid. Otherwise, the program should convert the length to inches and print out the result. There are 2.54 centimeters in an inch. Use ‘if-else’ statement.

Code: len = float(input('Enter length in centimeters: ')) if(len<0): print("The entry is invalid") else: inch=len/2.54 print("Equivalent length in inches is:", inch)

Examples

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Write a program that asks the user for two numbers and prints ‘Numbers are Close’ if the numbers are within 0.001 of each other and ‘Numbers are not close’ otherwise.

Code: n1 = float(input('Enter number 1: ')) n2 = float(input('Enter number 2: ')) if(n2-n1<=0.001): print("Numbers are close") else: print("Numbers are not close")

Examples

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Given three integers, determine how many of them are equal to each other. The program must print one of these numbers: 3 (if all are the same), 2 (if two of them are equal to each other and the third is different) or 0 (if all numbers are different)

Code: a = int(input()) b = int(input()) c = int(input()) if a == b == c: print(3) elif a == b or b == c or a == c: print(2) else: print(0)

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While - loop

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A while loop statement in Python programming language repeatedly executes a target statement as long as a given condition is true. Syntax: The syntax of a while loop while expression: statement(s)

Example – while loop

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count = 0 while (count < 9): print( 'The count is:', count) count = count + 1 print "Good bye!" When the above code is executed, it produces the following result − The count is: 0 The count is: 1 The count is: 2 The count is: 3 The count is: 4 The count is: 5 The count is: 6 The count is: 7 The count is: 8 Good bye!

Example - While - loop

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end=12 n=1 while(n<=end): print(n) Result : It will print 1 to infinite

end=12 n=1 while(n<=end): print(n) n = n+1 Result : It will print 1 to 12

While - loop

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Write a program to find the sum of the digits of a given number num=int(input("please enter the number")) x=num sum=0 rem=0 while(num>0): #while loop is used &last digit of number is obtained by rem=num%10 using modulus operator ,so it gives remainder num=num//10 # (123/10) it will gives only 12 number (gives only integer) sum=sum+rem # rem is added to variable sum each time the loop exexutes print("sum of the digits of an entered number",x,"is=",sum) Output: please enter the number123 sum of the digits of an entered number 123 is= 6

Note: The integer number is read from the user. And it is stored in variable num . Initially the value of sum and rem are initialized to 0. Unless and until the value of num>0 the statement within the loop continue to be executed. The modulus operator And division operator are used frequently to obtain the sum of the numbers enterd.

While - loop

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Write a program to print factorial of a number using while loop num=int(input("please enter the number:")) fact=1 ans=1 while(fact<=num): ans=ans*fact fact=fact+1 print("factorial of ",num," is: ",ans) Output: please enter the number:6 factorial of 6 is: 720

else: While - loop

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Python supports to have an else statement associated with a loop statement. If the else statement is used with a while loop, the else statement is executed when the condition becomes false.

count = 0 while count < 5: print (count, " is less than 5") count = count + 1 else: print (count, " is not less than 5") Result: 0 is less than 5 1 is less than 5 2 is less than 5 3 is less than 5 4 is less than 5 5 is not less than 5

While – loop - continue

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It returns the control to the beginning of the while loop. The continue statement rejects all the remaining statements in the current iteration of the loop and moves the control back to the top of the loop. The continue statement can be used in both while and for loops. Syntax: Continue

Flow Diagram :

Example: While – loop - continue

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var = 10 while var > 0: var = var -1 if var == 5: continue print ('Current variable value :', var) print ("Good bye!") Result: Current variable value : 9 Current variable value : 8 Current variable value : 7 Current variable value : 6 Current variable value : 4 Current variable value : 3 Current variable value : 2 Current variable value : 1 Current variable value : 0 Good bye!

Condi tion? True

Yes

Conti nue? No Body of loop

false Exit loop

While – loop - continue

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x=0 Note: Skip all statements below the continue statement while x < 5 : if(x==2): continue x = x+1 print("\nx =",x) print("This is statement 1 inside while loop ") print("This is statement 2 inside while loop ") print("This is statement 3 inside while loop ") print("This is statement 4 inside while loop ") else : print("\nThis is statement in else part of while ") print("\nThis is statement outside while loop ") Result : x=2 x=1 This is statement 1 inside while loop This is statement 1 inside while loop This is statement 2 inside while loop This is statement 2 inside while loop This is statement 3 inside while loop This is statement 3 inside while loop This is statement 4 inside while loop This is statement 4 inside while loop

Python break statement

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It terminates the current loop and resumes execution at the next statement, just like the traditional break statement in C. The break statement can be used in both while and for loops. If you are using nested loops, the break statement stops the execution of the innermost loop and start executing the next line of code after the block. Syntax: The syntax for a break statement in Python is as follows − break Flow Diagram:

Example: While – loop - break

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var = 10 # first Example while var > 0: print ('Current variable value :', var) var = var -1 if var == 5: break print ("Good bye!") Output: Current variable Current variable Current variable Current variable Current variable Good bye!

value : 10 value : 9 value : 8 value : 7 value : 6

Test conditi on

false

True True

Bre ak? false Body of loop

Exit loop

Example: While – loop - break

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x=0 while x < 5 : if(x==2): break x = x+1 print("\nx =",x) print("This is statement 1 inside while loop ") print("This is statement 2 inside while loop ") print("This is statement 3 inside while loop ") print("This is statement 4 inside while loop ") else : print("\nThis is statement in else part of while ") print("\nThis is statement outside while loop ") Result : x=2 x=1 This is statement 1 inside while loop This is statement 1 inside while loop This is statement 2 inside while loop This is statement 2 inside while loop This is statement 3 inside while loop This is statement 3 inside while loop This is statement 4 inside while loop This is statement 4 inside while loop This is statement outside while loop

The range( ) function

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There is inbuilt function in python called range( ) , which is used to generates a list of integers. The range has one, two or three parameters. The last two parameters are optional. The general form of range( ) function is range( start , end , step ) Default value of start is zero Default value of step is one • The ‘start’ is first beginning number in the sequence at which list starts •The ‘end’ is the limit , ie last number in the sequence •The ‘step’ is the difference between each number in the sequence. Example: range ( 0,n,1) Where n is end or stop element , then last element should be n-1 i.e 0 1 2 n-1

The range( ) function

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In python variable i will take the value from 1 to n-1 . e.g : for i in range(10): print(i) There are 3 way to write range function 1. range(end) 2. Range(start , end) 3. Range(start , end , step)

Note: If you don’t give start , default value is zero If you don’t give step , default value is one

Python for Loop Statements

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A statement that is executed sequentially and allow us to to execute group of statements multiple times. It has the ability to iterate over the items of any sequence, such as a list or a string. Syntax: for variable in sequence: statements(s) Val – is variable which takes the value of item inside sequence of n iteration Note : If a sequence contains an expression list, it is evaluated first. Then, the first item in the sequence is assigned to the iterating variable iterating_var. Next, the statements block is executed. Each item in the list is assigned to iterating_var, and the statement(s) block is executed until the entire sequence is

Flow diagram of for statement

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Flow Diagram:

Example using for loop

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1.for character in 'hello': print(character)

Output: h e l l o 2. for i in range(10): print(“Hello world”)

# 0 to 9

Output: hello world ( 10 times printed)

Example using for loop

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L = [ “ sachin” , Rahul”, “ Saurabh” ] for i in L : print(i) Output: Sachin Rahul Saurabh

Example using for loop

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# Table of 5 using for loop Code: for i in range(5,55,5): OR print(i)

for i in range(5,51,5): print(i)

Output: 5 10 15 20 25 30 35 40 45 50 Note : if last element is 51 to 55 then it print up to 50. if last element is less than 51 then it print up to 45. if last element is greater than 55 then it print up to 55.

Example using for loop

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# print even number between 20 to 40 using for loop Code: for i in range(20,40,2): print(i) Output: 20 22 24 26 28 30 32 34 36 38

Example using for loop

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Code: for i in range(2): print(i) i=i+50 print(i) Output: 0 50 1 51

Example using for loop

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Code: for i in range(10): print(i) i=i+50 print(i) Output: 0 50 1 51 2 52 3 53 ∣ ∣ ∣ 9 59

Example using for loop

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# print pattern ****** using for loop Code: for i in range(10): print('*****') Output: ***** ***** ***** ***** ***** ***** ***** ***** ***** *****

Example using for loop

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Code: for j in range(10): for i in range(j+1): print("*",end="") print() Output: * * * * * * * * * *

Example using for loop

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# print pyramid like pattern using for loop Code: for i in range(11): print( '*‘ *i ) Output: * ** *** **** ***** ****** ******* ******** ********* **********

Example using for loop

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# print pyramid like pattern using for loop Code: for i in range(10): print('*'*(10-i)) Output: ********** ********* ******** ******* ****** ***** **** *** ** *

for loop – integer variable

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Another use case for a for-loop is to iterate some integer variable in increasing or decreasing order. Such a sequence of integer can be created using the function range(min_value, max_value): Program: for i in range(5,8): print(i, i ** 2) print(‘end of loop’) Output: 5 25 6 36 7 49 end of loop Note: Function range(min_value, max_value) generates a sequence with numbers min_value, min_value + 1, ..., max_value - 1. The last number is not included

for loop with range

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There's a reduced form of range( ) - range(max_value), in which case min_value is implicitly set to zero: e.g. for i in range(3): print(i) Output : 0 1 2 Range( ) can define an empty sequence, like range(-5) or range(7, 3). In this case the for-block won't be executed: To iterate over a decreasing sequence, we can use an extended form of range( ) with three arguments - range(start_value, end_value, step). When omitted, the step is implicitly equal to 1. However, can be any non-zero value. The loop always includes start_value and excludes end_value during iteration: Output e.g. 10 for i in range(10, 0, -2): 8 print(i) 6 4 2

How to merge multiple print?

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print(1, 2, 3) print(4, 5, 6) Output: 123 456

print(1, 2, 3,end=',') print(4, 5, 6) Output 1 2 3,4 5 6

Example using for loop

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# print capital letters from A to Z using for loop Code: print(‘ The capital letters from A to Z is: ‘) for i in range(65,91,1): print(chr(i), end=‘ ‘) Output: The capital letters from A to Z is: A,B,C,……………Z # To print numbers from 1 to 10 in reverse order

Code: print(“ Numbers from 1 to 10 in Reverse order is: ”) for i in range(10,0,-1): print(i, end = ‘ ‘) Output: Numbers from 1 to 10 in Reverse order is: 10 9 8 7 ……1

for loop with range

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By default, the function print( ) prints all its arguments separating them by a space and the puts a newline symbol after it. This behavior can be changed using keyword arguments sep (separator) and end. e.g. print(1, 2, 3) Output print(4, 5, 6) 123 print(1, 2, 3, sep=', ', end='. ') 456 print(4, 5, 6, sep=', ', end='. ') 1, 2, 3. 4, 5, 6. print( ) 123 -- 4 * 5 * 6. print(1, 2, 3, sep=‘ ’, end=' -- ') print(4, 5, 6, sep=' * ', end='.')

for loop with break

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Problem: WAP using break statement to print first three letters in “string” for val in "string": if val=="i": break print(val)

Output: s t r

for loop with continue

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Problem: WAP using continue statement to print a “string” for val in "string": if val=="i": continue print(val)

Output: s t r n g

for loop with continue

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Problem: WAP using continue statement for i in range (1,10): if i== 5: continue print(i) print(”loop terminate”)

Output: 1 2 3 4 6 7 8 9

Python - Numbers

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Number data types store numeric values.

Python supports four different numerical types − 1.int (signed integers) − They are often called just integers or ints, are positive or negative whole numbers with no decimal point. 2.long (long integers ) − Also called longs, they are integers of unlimited size, written like integers and followed by an uppercase or lowercase L. 3.float (floating point real values) − Also called floats, they represent real numbers and are written with a decimal point dividing the integer and fractional parts. Floats may also be in scientific notation, with E or e indicating the power of 10 (2.5e2 = 2.5 x 102 = 250). 4.complex (complex numbers) − are of the form a + bJ, where a and b are floats and J (or j) represents the square root of -1 (which is an imaginary number). The real part of the number is a, and the imaginary part is b. Complex numbers are not used much in Python programming.

Mathematical Functions

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Function

Returns ( Description )

abs(x)

The absolute value of x: the (positive) distance between x and zero.

ceil(x)

The ceiling of x: the smallest integer not less than x.

cmp(x, y)

-1 if x < y, 0 if x == y, or 1 if x > y. Deprecated in Python 3. Instead use return (x>y)-(x
exp(x)

The exponential of x: ex

fabs(x)

The absolute value of x.

floor(x)

The floor of x: the largest integer not greater than x.

log(x)

The natural logarithm of x, for x > 0.

log10(x)

The base-10 logarithm of x for x > 0.

max(x1, x2,...)

The largest of its arguments: the value closest to positive infinity

min(x1, x2,...)

The smallest of its arguments: the value closest to negative infinity.

modf(x)

The fractional and integer parts of x in a two-item tuple. Both parts have the same sign as x. The integer part is returned as a float

Mathematical Functions

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Function

Returns ( Description )

pow(x, y)

The value of x**y.

round(x [,n])

x rounded to n digits from the decimal point. Python rounds away from zero as a tie-breaker: round(0.5) is 1.0 and round(-0.5) is 1.0.

sqrt(x)

The square root of x for x > 0.

Mathematical Functions/ math module

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1.Python Number abs() : The method abs() returns absolute value of x - the (positive) distance between x and zero. Syntax: Following is the syntax for abs() method − abs( x ) Parameters x − This is a numeric expression. Return Value This method returns absolute value of x. Example: print ("abs(-45) : ", abs(-45)) print ("abs(100.12) : ", abs(100.12)) print ("abs(119) : ", abs(119)) Output: abs(-45) : 45 abs(100.12) : 100.12 abs(119) : 119

Mathematical Functions

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Description The fabs( ) method returns the absolute value of x. Although similar to the abs() function, there are differences between the two functions. They are − •abs( ) is a built in function whereas fabs( ) is defined in math module. •fabs( ) function works only on float and integer whereas abs( ) works with complex number also. import math # This will import math module print ("math.fabs(-45.17) : ", math.fabs(-45.17)) print ("math.fabs(100.12) : ", math.fabs(100.12)) print ("math.fabs(100.72) : ", math.fabs(100.72)) print ("math.fabs(math.pi) : ", math.fabs(math.pi)) Output math.fabs(-45.17) : 45.17 math.fabs(100.12) : 100.12 math.fabs(100.72) : 100.72 math.fabs(math.pi) : 3.141592653589793

Mathematical Functions

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ceil() function : Description The method ceil() returns ceiling value of x - the smallest integer not less than x. Python has many auxiliary functions for calculations with floats. They can be found in the math module. To use this module, we need to import it first by writing the following instruction at the beginning of the program: import math Syntax Following is the syntax for ceil() method − import math math.ceil( x ) Example: import math print("math.ceil(-45.17) : ", math.ceil(-45.17)) print("math.ceil(100.12) : ", math.ceil(100.12)) print("math.ceil(100.72) : ", math.ceil(100.72)) Output: math.ceil(-45.17) : -45 math.ceil(100.12) : 101 math.ceil(100.72) : 101

exp()

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Description: The method exp() returns exponential of x: ex. Syntax Following is the syntax for exp() method − import math math.exp( x ) Example : print("math.exp(2) : ", math.exp(2)) print ("math.exp(100.12) : ", math.exp(100.12)) Output: math.exp(2) : 7.38905609893065 math.exp(100.12) : 3.0308436140742566e+43

floor()

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Description The method floor() returns floor of x - the largest integer not greater than x. Syntax Following is the syntax for floor() method − import math math.floor( x )

Example: import math print ("math.floor(-45.17) : ", math.floor(-45.17)) print ("math.floor(100.12) : ", math.floor(100.12)) Output: math.floor(-45.17) : -46 math.floor(100.12) : 100

log()

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Description: The method log( ) returns natural logarithm of x, for x > 0. Syntax: Following is the syntax for log() method − import math math.log( x ) Example: import math print ("math.log(1) : ", math.log(1)) print ("math.log(100.12) : ", math.log(100.12)) Output: math.log(1) : 0.0 math.log(100.12) : 4.6063694665635735

sqrt()

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Description: The method sqrt() returns the square root of x for x > 0. Syntax: Following is the syntax for sqrt() method − import math math.sqrt( x )

Example: import math print ("math.sqrt(100) : ", math.sqrt(100)) print ("math.sqrt(7) : ", math.sqrt(7)) Output: math.sqrt(100) : 10.0 math.sqrt(7) : 2.6457513110645907

pow()

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This method returns value of xy. Syntax: math.pow(x,y) Example: import math print ("math.pow(5, 2) : ", math.pow(5, 2)) print ("math.pow(100, 2) : ", math.pow(100, 2)) Output: math.pow(5, 2) : 25.0 math.pow(100, 2) : 10000.0

Mathematical Functions

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print ("round(70.23456) : ", round(70.23456)) print ("round(56.659,1) : ", round(56.659,1)) print ("round(80.264, 2) : ", round(80.264, 2)) print ("round(100.000056, 3) : ", round(100.000056, 3)) print ("round(-100.000056, 3) : ", round(-100.000056, 3))

Output round(70.23456) : 70 round(56.659,1) : 56.7 round(80.264, 2) : 80.26 round(100.000056, 3) : 100.0 round(-100.000056, 3) : -100.0

Description

The sqrt( ) method returns the square root of x for x > 0. Syntax import math Output math.sqrt( x ) math.sqrt(100) : 10.0 math.sqrt(7) : 2.6457513110645907 print ("math.sqrt(100) : ", math.sqrt(100)) math.sqrt(math.pi) : 1.772453850905515 print ("math.sqrt(7) : ", math.sqrt(7)) print ("math.sqrt(math.pi) : ", math.sqrt(math.pi)) Description The randrange( ) method returns a randomly selected element from range(start, stop, step). Syntax randrange ([start,] stop [,step])

Mathematical Functions – max( )

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Description The max( ) method returns the largest of its arguments i.e. the value closest to positive infinity. Syntax max( x, y, z, .... ) # x,y,z are numeric expression print ("max(80, 100, 1000) : ", max(80, 100, 1000)) print ("max(-20, 100, 400) : ", max(-20, 100, 400)) print ("max(-80, -20, -10) : ", max(-80, -20, -10)) print ("max(0, 100, -400) : ", max(0, 100, -400))

Output max(80, 100, 1000) : 1000 max(-20, 100, 400) : 400 max(-80, -20, -10) : -10 max(0, 100, -400) : 100

Description The method min( ) returns the smallest of its arguments i.e. the value closest to negative infinity.

Random number function

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import random # randomly select an odd number between 1-100 print ("randrange(1,100, 2) : ", random.randrange(1, 100, 2)) # randomly select a number between 0-99 print ("randrange(100) : ", random.randrange(100)) Output randrange(1,100, 2) : 83 randrange(100) : 93 The seed( ) method initializes the basic random number generator. Call this function before calling any other random module function. Syntax seed ([x], [y]) import random random.seed() print ("random number with default seed", random.random()) random.seed(10) print ("random number with int seed",random.random()) random.seed("hello",2) print ("random number with string seed", random.random())

Random number function

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Description The shuffle( ) method randomizes the items of a list in place. Syntax shuffle (lst,[random])

import random list = [20, 16, 10, 5]; random.shuffle(list) print ("Reshuffled list : ", list) random.shuffle(list) print ("Reshuffled list : ", list) Description The uniform( ) method returns a random float r, such that x is less than or equal to r and r is less than y. Syntax uniform(x, y)

Trigonometric Functions -sin()

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Description The method sin() returns the sine of x, in radians. Syntax Following is the syntax for sin() method − math.sin(x) Example: import math print ("sin(3) : ", math.sin(3)) print ("sin(-3) : ", math.sin(-3)) print ("sin(0) : ", math.sin(0)) Output: sin(3) : 0.1411200080598672 sin(-3) : -0.1411200080598672 sin(0) : 0.0

cos()

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Description: The method cos( ) returns the cosine of x radians. Syntax: Following is the syntax for cos() method − cos(x)

Example: print ("cos(3) : ", math.cos(3)) print ("cos(-3) : ", math.cos(-3)) print ("cos(0) : ", math.cos(0)) Output: cos(3) : -0.9899924966004454 cos(-3) : -0.9899924966004454 cos(0) : 1.0

tan()

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Description: The method tan() returns the tangent of x radians. Syntax: Following is the syntax for tan() method − tan(x) Example: import math print ("tan(3) : ", math.tan(3)) print ("tan(-3) : ", math.tan(-3)) print ("tan(0) : ", math.tan(0)) Output: tan(3) : -0.1425465430742778 tan(-3) : 0.1425465430742778 tan(0) : 0.0

degrees() Method

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Description The method degrees() converts angle x from radians to degrees. Syntax Following is the syntax for degrees() method − degrees(x) Note: This method returns degree value of an angle. Example: print ("degrees(3) : ", math.degrees(3)) print ("degrees(-3) : ", math.degrees(-3)) print ("degrees(0) : ", math.degrees(0)) print ("degrees(math.pi) : ", math.degrees(math.pi)) print ("degrees(math.pi/2) : ", math.degrees(math.pi/2)) Output: degrees(3) : 171.88733853924697 degrees(-3) : -171.88733853924697 degrees(0) : 0.0 degrees(math.pi) : 180.0 degrees(math.pi/2) : 90.0

radians() Method

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Description The method radians() converts angle x from degrees to radians. Syntax Following is the syntax for radians() method − radians(x) Note: This method returns radian value of an angle. Example: import math print ("radians(3) : ", math.radians(3)) print ("radians(math.pi) : ", math.radians(math.pi)) Output: radians(3) : 0.05235987755982989 radians(math.pi) : 0.05483113556160755

Random Number Functions

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Random numbers are used for games, simulations, testing, security, and privacy applications. Python includes following functions that are commonly used. Function Description 1.choice(seq) A random item from a list, tuple, or string. 2.randrange ([start,] stop [,step]) A randomly selected element from range(start, stop, step) 3.random()A random float r, such that 0 is less than or equal to r and r is less than 1 4.seed([x])Sets the integer starting value used in generating random numbers. Call this function before calling any other random module function. Returns None. 5.shuffle(lst)Randomizes the items of a list in place. Returns None. 6.uniform(x, y)A random float r, such that x is less than or equal to r and r is less than y

Python Strings

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String : Any program is composed of sequence of characters. When a sequence of characters are grouped together , a string is created.  String in python are surrounded by either single quotation marks, or double quotation marks. 'hello' is the same as "hello".  Strings can be output to screen using the print function. For example: print("hello").  In many programming language , strings are treated as arrays of characters but in python a string is an object of the str class.  Like many other popular programming languages, strings in Python are arrays of bytes representing unicode characters. However, Python does not have a character data type, a single character is simply a string with a length of 1. Square brackets can be used to access elements of the string.

Python Strings- object

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We can create a string using the str class as: s1 = str( ) # create an empty string object s2 = str(“Hello”) # create an string object for Hello

OR An alternative way to create a string object is by assigning a string value to a variable. Example: s1 = “ “ # create an empty string s2 = “Hello” # Equivalent to s2 = str(“Hello”)

How to access character in a string?

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Index[ ] operator: As string is a sequence of characters . The characters in a string can be accessed one at a time through the index operator. The first character of the string is stored at the 0 th position and last character of the string is stored at a position one less than that of the length of the string. For the string Sammy Shark! the index breakdown looks like this:

As you can see, the first S starts at index 0, and the string ends at index 11 with the ! symbol. We also notice that the whitespace character between Sammy and Shark also corresponds with its own index number. In this case, the index number associated with the whitespace is 5. The exclamation point (!) also has an index number associated with it. Any other symbol or punctuation mark, such as *#$&.;?, is also a character and would be associated with its own index number.

Example

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Example: >>> s1="python" >>>s1[0] >>>s1[5]

# Access the first element of the string # Access the last element of the string

Accessing characters via Negative index

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If we have a long string and we want to pinpoint an item towards the end, we can also count backwards from the end of the string, starting at the index number -1.

Example- Initialization

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Directly write string name String = “hello” Here index is always start from 0 to n-1 , where n is length of string . Syntax: String[index] where index = index of any mathematical expression

Example: string = “hello” string[0] = h string[1] = e string[2] = l string[3] = l string[4] = o

Traversing string with for & while loop

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A programmer can use the for loop to traverse all characters in a string. Code: Write a program to traverse all elements of a string using for loop Example: s =“ India” for ch in s: print(ch , end = “ ”) Output: India Explanation: The string ‘India’ is assigned to variable s. The for loop is used to print all the character of a string s. The statement ‘for ch in s:’ can read as ‘for each character ch in s print ch’

Traversing string with for & while loop

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A programmer can use the for loop to traverse all characters in a string. Code: Write a program to traverse every second character of a string using for loop Example: s =“ ILOVEPYTHONPROGRAMMING” for ch in range(0,len(s),2): # Traverse each second character print(s[ch] , end = “ ”) Output: I 0 E YH N R GAM N Example: for ch in range(1,len(s),2): print(s[ch] , end = " ") Output: LVPTOPOR MIG

Traversing string with while loop

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A programmer can use the while loop to traverse all characters in a string. Example: s =“ India” Index = 0 While index< len(s): print(s[index] , end = “ ”) index = index+1 Output: India

Slices: single character

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A slice gives from the given string one character or some fragment: substring or subsequence. There are three forms of slices. The simplest form of the slice: a single character slice S[i] gives ith character of the string. We count characters starting from 0. That is, if S = 'Hello', S[0] == 'H', S[1] == 'e', S[2] == 'l',S[3] == 'l', S[4] == 'o'. Note that in Python there is no separate type for characters of the string. S[i] also has the type str, just as the source string. Number i in S[i] is called an index. If you specify a negative index, then it is counted from the end, starting with the number -1. That is, S[-1] == 'o', S[-2] == 'l', S[-3] == 'l', S[-4] == 'e', S[-5] == 'H'. Let's summarize it in the table:

Strings operators- Accessing substring

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String contains the slicing operator and the slicing with step size parameter is used to obtain the subset of string. String slicing operator[ start :end ] The slicing operator returns a subset of a string called slice by specifying two indices , start and end . Syntax : Name of variable of a string[ Start index : End index ] Example : s=Hello" print(s[1:4])

# The s[1:4] returns a subset of string starting from start index 1 to one index less than that of end parameter of slicing operation (4-1=3)

Output : ell Note : we can get the same substring using S[-4:-1] we can mix positive and negative indexes in the same slice, for example, S[1:-1] is a substring without the first and the last character of the string

Strings operators- Accessing substring

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For example : if s == 'Hello' the slice S[1:5] returns the string 'ello', and the result is the same even if the second index is very large, like S[1:100].

Strings slice with step size

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We learnt , how to select a portion of string. But how does a programmer select every second character from a string ? This can be done by using step size. In slicing first two parameters are start and end. We need to add a third parameter as step size to select the character from a string with step size. Syntax: Name of variable of a string[ Start _ index : End _ index: step_ size ] Example: s="IIT-MADRAS" print(s[0:len(s):2]) Output: ITMDA

Some more complex example of string slicing

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For example : s = “ IIT-MADRAS” 1. s="IIT-MADRAS" print(s[: :]) output : IIT-MADRAS # print entire string 2. print(s[1:]) output: IT-MADRAS 3. print(s[:3]) output: IIT 4. print(s[:-1]) # start with index 0 and exclude last output: IIT-MADRA character stored at index-1. 5. print(s[1:-1]) output : IT-MADRA 6. print( s[: : 2] ) or print ( s[ 0: : 2] ) output: ITMDA #alternate characters are printed 7. print(s[::-1] output : SARDAM-TII # display the string in reverse order 8. print(s[-1:0:-1]) output : SARDAM-TI # Access the character from -1 9. print(s[1::2]) output: I-ARS

String character sequence

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String character sequence is divided in to two categories 1. Mutable : mutable means changeable 2. Immutable : mutable means unchangeable

Note: strings are immutable sequence of characters. Let us see what happens if we try to change the contents of the string. Example : str1="I Love Python" str1[0]="U" print(str1) Output : TypeError: 'str' object does not support item assignment Explanation : here we have assigned the string “I Love Python“ to str1. The index [ ] operator is used to change the contents of the string. Finally it show an error because the strings are immutable ( can not change the existing string).

Solution - String character sequence

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If you want to change the existing string, the best way is to create a new string that is a variation of original string. Example: str1="I LOVE PYTHON" str2="U"+str1[1:] print(str2) Output: U LOVE PYTHON

How to concatenate and repetition of a string?

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Two strings can be concatenated by using + operator Example: str1=“Hello" str2=“python” print(str1+str2) Output: Hellopython Note: print(str1+2 ) – Not allowed , it gives error we can also repeat a string n times multiplying it by integer Example: str1=“Hello“ print(str1*3) Output: HelloHelloHello Note : print( str1*str2) - Not allowed , it gives error

String methods/ String function

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A method is a function that is bound to the object. When the method is called, the method is applied to the object and does some computations related to it. The syntax of methods are invoked as object t_ name. method _ name(arguments) 1. find Method: It determines if string str occurs in string, or in a substring of string if starting index beg and ending index end are given. Syntax: string_name.find(arguments) Note: It returns Index if found and -1 otherwise. Example : output : 1 s = 'Hello‘ 2 print(s.find('e')) -1 print(s.find('ll')) print(s.find('L'))

String methods:

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Similarly, the method rfind() returns the index of the last occurrence of the substring. Example: s = 'abracadabra' print(s.find('b')) Output : 1 print(s.rfind('b')) Output : 8

Split Method

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



The method split() returns a list of all the words in the string , using str as the separator. Basically create a list with elements of given string separated by space.

Example: str="welcome to python" print(str. split( )) Output : ['welcome', 'to', 'python']

string function capitalize( ), center( )

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Syntax

Output str.capitalize( ) : This is string example....wow!!!

str.capitalize( ) str = "this is string example....wow!!!" print ("str.capitalize( ) : ", str.capitalize( )) The method center( ) returns centered in a string of length width. Syntax. str.center(width, fillchar) Parameters width − This is the total width of the string. fillchar − This is the filler character. b="hello" print(b.center(11,"x")) Output xxxhelloxxx

# hello is at center , left and right hand side of hello it filled with character x

center( )

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Example: b="hello welcome to python programming" print(b.center(11,"x")) Output : hello welcome to python programming Note: here actual width of a string b is greater than 11. Hence it will print hello welcome to python programming string.

Function find( )

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Description The find( ) method determines if the string str occurs in string, or in a substring of string if the starting index beg and ending index end are given. Syntax str.find(str, beg = 0 end = len(string)) Parameters str − This specifies the string to be searched. beg − This is the starting index, by default its 0. end − This is the ending index, by default its equal to the length of the string. e.g. b="hello welcome to python programming" print(b.find("o",0,len(b))) Output: 4 It return the index value of first occurrence of “o”

Function split

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Description The split( ) method returns a list of all the words in the string, using str as the separator (splits on all whitespace if left unspecified), optionally limiting the number of splits to num. Syntax str.split(str=" ", num = string.count(str)). Parameters str − This is any delimeter, by default it is space. num − this is number of lines to be made e.g. str = "this is string example....wow!!!" print (str.split( )) Output print (str.split( 'i',1)) ['this', 'is', 'string', 'example....wow!!!'] print (str.split('w')) ['th', 's is string example....wow!!!'] ['this is string example....', 'o', '!!!']

String Formatting Operator

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One of Python's coolest features is the string format operator %. This operator is unique to strings and makes up for the pack of having functions from C's printf( ) family. e.g. print ("My name is %s and weight is %d kg!" % ('Zara', 21))

Output My name is Zara and weight is 21 kg! Most complex format: python3 added a new string method called format( ) method. Instead of %s we can use {0}, {1} and so on Syntax: template.format(p0,p1,…..) e.g. print ("My name is {0} and weight is {1} kg!“.format ('Zara', 21)) Output My name is Zara and weight is 21 kg!

Format Symbol & Conversion

VI %c  character %s  string conversion via str() prior to formatting %i  signed decimal integer %d  signed decimal integer %u  unsigned decimal integer %o  octal integer %x  hexadecimal integer (lowercase letters)

Format Symbol & Conversion

VI

%X  hexadecimal integer (UPPERcase letters) %e  exponential notation (with lowercase 'e') %E  exponential notation (with UPPERcase 'E') %f  floating point real number %g  the shorter of %f and %e %G  the shorter of %f and %E

Function Index

VI

Description The index( ) method determines if the string str occurs in string or in a substring of string, if the starting index beg and ending index end are given. Syntax

str.index(str, beg = 0 end = len(string))

Parameters •str − This specifies the string to be searched. •beg − This is the starting index, by default its 0. •end − This is the ending index, by default its equal to the length of the string.

e.g. str1 = "this is string example....wow!!!“ str2 = "exam"; print (str1.index(str2)) print (str1.index(str2, 10)) print (str1.index(str2, 40))

Output 15 15 Traceback (most recent call last):

Function islower( ),len( )

VI

Description The islower( ) method checks whether all the case-based characters (letters) of the string are lowercase. Syntax str.islower( ) e.g. str = "THIS is string example....wow!!!" print (str.islower( )) str = "this is string example....wow!!!“ print (str.islower( ))

Output False True

Description The len( ) method returns the length of the string. Syntax len( str ) e.g. str = "this is string example....wow!!!" print ("Length of the string: ", len(str))

Output Length of the string: 32

Function lower( )

VI

Description The method lower() returns a copy of the string in which all case-based characters have been lowercased.

Syntax str.lower( ) Return Value This method returns a copy of the string in which all case-based characters have been lowercased. e.g. str = "THIS IS STRING EXAMPLE....WOW!!!" print (str.lower( )) Output this is string example....wow!!!

Function replace( )

VI

Description The replace( ) method returns a copy of the string in which the occurrences of old have been replaced with new, optionally restricting the number of replacements to max. Syntax str.replace(old, new, max) Parameters •old − This is old substring to be replaced. •new − This is new substring, which would replace old substring. •max − If this optional argument max is given, only the first count occurrences are replaced. e.g. str = "this is string example....wow!!! this is really string“ print (str.replace("is", "was")) print (str.replace("is", "was", 3)) Output thwas was string example....wow!!! thwas was really string thwas was string example....wow!!! thwas is really string

Function : count()

VI

Description

This method counts the number of occurrences of one string within another string. Syntax

s.count(substring) Note : Only non-overlapping occurrences are taken into account e.g. print('Abracadabra'.count('a')) print(('aaaaaaaaaa').count('aa'))

Output

4 5

list

VI



The most basic data structure in Python is the sequence. Each element of a sequence is assigned a number - its position or index. The first index is zero, the second index is one, and so forth.



There are certain things you can do with all the sequence types. These operations include indexing, slicing, adding, multiplying, and checking for membership. In addition, Python has built-in functions for finding the length of a sequence and for finding its largest and smallest elements.



There are certain things you can do with all the sequence types. These operations include indexing, slicing, adding, multiplying, and checking for membership. In addition, Python has built-in functions for finding the length of a sequence and for finding its largest and smallest elements.

list

VI

Python Lists The list is the most versatile data type available in Python, which can be written as a list of comma-separated values (items) between square brackets. Important thing about a list is that the items in a list need not be of the same type. • Creating a list is as simple as putting different comma-separated values between square brackets. • e.g. list1 = ['physics', 'chemistry', 1997, 2000] list2 = [1, 2, 3, 4, 5, 6, 7 ] print ("list1[0]: ", list1[0]) print ("list2[1:5]: ", list2[1:5]) •

Output list1[0]: physics list2[1:5]: [2, 3, 4, 5]

Updating Lists

VI

You can update single or multiple elements of lists by giving the slice on the lefthand side of the assignment operator, and you can add to elements in a list with the append( ) method.  1. Append the element seq = [ 10,20,30,40 ] print( seq.append ( 50 ) Output : [ 10,20,30,40,50 ] 2. Reassign the element list = ['physics', 'chemistry', 1997, 2000] print ("Value available at index 2 : ", list[2]) list[2] = 2001 Print ( list ) 

Output: Value available at index 2 : 1997 list = ['physics', 'chemistry', 2001, 2000 ]

Delete List Elements

VI

To remove a list element, you can use either the del statement if you know exactly which element(s) you are deleting. You can use the remove() method if you do not know exactly which items to delete. list = ['physics', 'chemistry', 1997, 2000] print (list) del list[2] print ("After deleting value at index 2 : ", list) Output ['physics', 'chemistry', 1997, 2000] After deleting value at index 2 : ['physics', 'chemistry', 2000] Basic List Operations Python Expression

Results

Description

len([1, 2, 3])

3

Length

[1, 2, 3] + [4, 5, 6]

[1, 2, 3, 4, 5, 6]

Concatenation

['Hi!'] * 4

['Hi!', 'Hi!', 'Hi!', 'Hi!']

Repetition

List Slicing

VI

The slicing operator returns a subset of a list called slice by specifying two arguments start, end . Syntax : Name of list[start index : End index] Example: L1 = [ 10,20,30,40,50] L1[ 1:4] Output : [20,30,40 ]

List Slicing with step size

VI

We learnt how to select a portion of a list. In this , we will explore how to select every second or third element of a list using step size. Hence we need to add a third parameter a step size . Syntax : Name of list[start index : End index: step size] Example: mylist=["Hello",1,"Monkey",2,"Dog",3,"Donkey" ] newlist=mylist[0:6:2] or newlist=mylist[0: len(mylist) :2] print(newlist) Output : ['Hello', 'Monkey', 'Dog'] Example: mylist=["python",450,"c",300,"c++",670 ] newlist=mylist[0:6:3] print(newlist) Output : ['python', 300]

Python inbuilt functions for Lists

VI

len( ) Method : Description The method len() returns the number of elements in the list. Syntax: len(list) Example list1, list2 = [123, 'xyz', 'zara'], [456, 'abc'] print "First list length : ", len(list1) print "Second list length : ", len(list2) Output: first list length : 3 Second list length : 2

Python inbuilt functions for Lists

VI

max( ) Method Description The method max returns the elements from the list with maximum value. Syntax max(list) Example: list1, list2 = [‘123’, 'xyz', 'zara', 'abc'], [456, 700, 200] print ("Max value element : ", max(list1)) print ("Max value element : ", max(list2)) Output: Max value element : zara Max value element : 700 Example: list=['a','ab'] print(max(list)) Output: ab Example: list=['a','100'] print(max(list)) Output: a

Python inbuilt functions for Lists

VI

min() Method Description The method min returns the elements from the list with minimum value. Syntax min(list) Example: list1, list2 = [123, 'xyz', 'zara', 'abc'], [456, 700, 200] print "Min value element : ", min(list1) print "Min value element : ", min(list2) Output: Min value element : 123 Min value element : 200

Python inbuilt functions for Lists

VI

append() Method Description The method append() appends a passed obj into the existing list. Syntax list. append(obj) Example: list = [123, 'xyz', 'zara', 'abc'] list. append( 2009 ) print("Updated List : ", list) Output: Updated List : [123, 'xyz', 'zara', 'abc', 2009]

Python inbuilt functions for Lists

VI

extend() Method Description The method extend() appends a passed obj into the existing list. Syntax list. extend(seq) Example: List1 = [123, 'xyz', 'zara', 'abc', 123] List2 = [2009, ‘sara'] List1.extend(List2) print("Extended List : ", List1) Output: Extended List : [123, 'xyz', 'zara', 'abc', 123, 2009, ‘sara']

Python inbuilt functions for Lists

VI

index() Method Description The method index() returns the lowest index in list or which appear first in the list. Syntax list.index(obj) Example: List = [123, 'xyz', 'zara', 'abc']; print ("Index for xyz : ", List.index( 'xyz' )) print ("Index for zara : ", List.index( 'zara' )) Output: Index for xyz : 1 Index for zara : 2 Example : seq = [1,2,3,4,5 ] print(“Index for 4:” , seq. index(4)) Output: 3

Python inbuilt functions for Lists

VI

insert() Method Description The method insert() inserts object or element at particular index position Syntax list. insert(index, obj) Where , index − This is the Index where the object or element need to be inserted. obj − This is the Object or element to be inserted into the given list Example: aList = [123, 'xyz', 'zara', 'abc'] aList.insert( 3, 2009) # insert element 2009 at index 3 print ("Final List : ", aList) Output: Final List : [123, 'xyz', 'zara', 2009, 'abc']

Python inbuilt functions for Lists

VI

pop( ) Method Description The method pop( ) removes and returns last object or element from the list. Syntax list.pop(obj) Example: aList = [123, 'xyz', 'zara', 'abc'] print("A List : ", aList.pop( )) print("B List : ", aList.pop(2)) Output: A List : abc B List : zara

Python inbuilt functions for Lists

VI

remove( ) Method Description The method remove( ) removes the first occurrence of given value from the given list. Syntax list. remove(obj ) Example: aList = [123, 'xyz', 'zara', 'abc', 'xyz']; aList.remove('xyz'); print("List : ", aList) aList.remove('abc'); print("List : ", aList) Output: List : [123, 'zara', 'abc', 'xyz'] List : [123, 'zara', 'xyz']

Python inbuilt functions for Lists

VI

reverse( ) Method Description The method reverse( ) reverses objects or element of list. Syntax list. reverse( ) Example: aList = [123, 'xyz', 'zara', 'abc', 'xyz']; aList.reverse(); print ("List : ", aList)

Output: List : ['xyz', 'abc', 'zara', 'xyz', 123]

Python inbuilt functions for Lists

VI

sort( ) Method Description The method sort() sorts objects or element of list in ascending order. Syntax list.sort( ) # No arguments required Example: aList = [123, 'xyz', 'zara', 'abc', 'xyz']; aList.sort(); print("List : ", aList) Output: List : [123, 'abc', 'xyz', 'xyz', 'zara'] Example: seq = [ 1,2,3,1,4,1,5] print( seq.sort( ) ) Output: [ 1,1,1,2,3,4,5]

Python inbuilt functions for Lists

VI

sort( ) Method Description The method sort() sorts objects or element of list in ascending order. Syntax list.sort( ) # No arguments required Example: aList = [‘123’, 'xyz', 'zara', 'abc', 'xyz']; aList.sort(); print("List : ", aList) Output: List : [123, 'abc', 'xyz', 'xyz', 'zara'] Example: seq = [ 1,2,3,1,4,1,5] print( seq.sort( ) ) Output: [ 1,1,1,2,3,4,5]

List Comprehensions

VI

List comprehension is used to create a new list from existing sequences. Syntax: [<expression> for < element >in < sequence > if < condition > ] It is read as “ Compute the expression for each element in the sequence, if the condition is true” Example: Create a list to store five different numbers such as 10,20,30,40 and 50.using the for loop, add number 5 to the existing elements of the list. without list comprehension : list[10,20,30,40,50 ] With list comprehension : Print(list) list=[10,20,30,40,50] Output: list=[x+5 for x in list] [10,20,30,40,50 ] print(list) for i in range(0,len(list)): Output: list[i] = list[i]+5 [15, 25, 35, 45, 55] print(list) Output: [15,25,35,45,55]

List Comprehensions

VI

Case 1. without list comprehension Example: list[10,20,30,40,50 ] Print(list) Output: [10,20,30,40,50 ] for i in range(0,len(list)): list[i] = list[i]+10 print(list) Output: [20,30,40,50,60]

Case 2. with list comprehension Example: list[10,20,30,40,50 ] list=[x+10 for x in list] print(list) Output: [20,30,40,50,60]

List Comprehensions

VI

Example: square = [i**2 for i in range(1,6)] print(square) Output : [1, 4, 9, 16, 25]

List Comprehensions

VI

With reference to above example we can say that list comprehension contains : 1. An input sequence 2. A variable referring the input sequence 3. An optional expression 4. An output expression or output variable. Example : list[10,20,30,40,50] list=[x+10 for x in list ] An output variable A variable referring an input sequence

An input sequence

Some problems statement

VI

1. Python Program to Calculate the Average of Numbers in a Given List Problem Description The program takes the elements of the list one by one and displays the average of the elements of the list. Problem Solution 1. Take the number of elements to be stored in the list as input. 2. Use a for loop to input elements into the list. 3. Calculate the total sum of elements in the list. 4. Divide the sum by total number of elements in the list. 5. Exit. Program/Source Code Here is source code of the Python Program to Calculate the Average of Numbers in a Given List. The program output is also shown below. n=int(input("Enter the number of elements to be inserted: ")) a=[ ] for i in range(0,n): elem=int(input("Enter element: ")) a.append(elem) avg=sum(a)/n print("Average of elements in the list",round(avg,2)) # rounds the average up to 2 decimal places.

Some problems statement

VI

2. Python Program to Find the Largest Number in a List Problem Description The program takes a list and prints the largest number in the list. Problem Solution 1. Take in the number of elements and store it in a variable. 2. Take in the elements of the list one by one. 3. Sort the list in ascending order. 4. Print the last element of the list. 5. Exit. Code: a=[ ] n=int(input("Enter number of elements:")) for i in range(1,n+1): b=int(input("Enter element:")) a.append(b) a.sort() print("Largest element is:",a[n-1])

Some problems statement

VI

3. Python Program to Find the smallest Number in a List Problem Description The program takes a list and prints the smallest number in the list. Code: a=[ ] n=int(input("Enter number of elements:")) for i in range(0,n): b=int(input("Enter element:")) a.append(b) a.sort(reverse=True) print("Largest element is:",a[n-1])

Some problems statement

VI

4. Python Program to Put Even and Odd elements in a List into Two Different Lists Problem Solution 1. Take in the number of elements and store it in a variable. 2. Take in the elements of the list one by one. 3. Use a for loop to traverse through the elements of the list and an if statement to check if the element is even or odd. 4. If the element is even, append it to a separate list and if it is odd, append it to a different one. 5. Display the elements in both the lists. 6. Exit. Code: a=[ ] n=int(input("Enter number of elements:")) for i in range(1,n+1): b=int(input("Enter element:")) a.append(b) even=[ ] else: odd=[ ] odd.append(j) for j in a: print("The even list",even) if(j%2==0): print("The odd list",odd) even.append(j)

Some problems statement

VI

5. WAP to check whether enter string is palindrome or not Code: string=input("Enter the string") revstr=string[::-1] if string==revstr: print("string is palindrome") else: print("string is not palindrome")

input : madam Output: madam

Some problems statement

VI

1.Write a program to create a list with elements 1,2,3,4,5.Display even elements of list using list compression. 2. Write a program to create a list ‘A’ to generate sequence of a number (from 1 to 10),list ‘B’ to generate cubes of a number (from 1 to 10) and list ‘C’ with those elements that are even and present in list ‘A’ 3. Write the values of ‘a’ for the given code. a=[1,2,3,4,5,6,7,8,9] a[::2]=10,20,30,40,50 print(a)

Output: [10, 2, 20, 4, 30, 6, 40, 8, 50]

Tuple

VI

A tuple is a sequence of immutable Python objects. Tuples are sequences, just like lists. The main difference between the tuples and the lists is that the tuples cannot be changed unlike lists. Tuples use parentheses, whereas lists use square brackets. Creating a tuple is as simple as putting different comma-separated values. Optionally, you can put these comma-separated values between parentheses also. tup1 = ('physics', 'chemistry', 1997, 2000) tup2 = (1, 2, 3, 4, 5 ) tup3 = "a", "b", "c", "d"  The empty tuple is written as two parentheses containing nothing tup1 = ( ); To write a tuple containing a single value you have to include a comma, even though there is only one value − tup1 = (50,) Like string indices, tuple indices start at 0, and they can be sliced, concatenated, and so on.

Accessing Values in Tuples and Updating Tuples

VI

To access values in tuple, use the square brackets for slicing along with the index or indices to obtain the value available at that index. tup1 = ('physics', 'chemistry', 1997, 2000) tup2 = (1, 2, 3, 4, 5, 6, 7 ) print ("tup1[0]: ", tup1[0]) print ("tup2[1:5]: ", tup2[1:5])

Output tup1[0]: physics tup2[1:5]: (2, 3, 4, 5)

Tuples are immutable, which means you cannot update or change the values of tuple elements. You are able to take portions of the existing tuples to create new tuples tup1 = (12, 34.56) tup2 = ('abc', 'xyz') # Following action is not valid for tuples # tup1[0] = 100; # So let's create a new tuple as follows tup3 = tup1 + tup2 print (tup3)

Output (12, 34.56, 'abc', 'xyz')

Delete Tuple, Indexing and Slicing

VI

Removing individual tuple elements is not possible. There is, of course, nothing wrong with putting together another tuple with the undesired elements discarded. To explicitly remove an entire tuple, just use the del statement. tup = ('physics', 'chemistry', 1997, 2000); print (tup) del tup; print ("After deleting tup : ") print (tup) T=('C++', 'Java', 'Python') Python Expression

Results

Description

T[2]

'Python'

Offsets start at zero

T[-2]

'Java'

Negative: count from the right

T[1:]

('Java', 'Python')

Slicing fetches sections

Tuple functions

VI

Sr.No .

Function & Description

1

len(tuple)Gives the total length of the tuple.

2

max(tuple)Returns item from the tuple with max value.

3

min(tuple)Returns item from the tuple with min value.

Exercise on List

VI

l1=['abc',[(1,2),([3],4)],5] print(l1[1]) print(l1[1][1][0]) print(l1[1][1][0][0])

Python Program to Find the Largest Number in a List. Python Program to Find the Second Largest Number in a List. Python Program to Put Even and Odd elements in a List into Two Different Lists.

Function

VI

A function is a block of organized, reusable code that is used to perform a single, related action . As you already know, Python gives you many built-in functions like print(), etc. but you can also create your own functions. These functions are called user-defined functions. simple rules to define a function in Python : 1. Every function should start with def keywords 2. Every function should have a name ( not equal to keyword) 3.parameters/ arguments included between parentheses 4. Every function name with or without arguments should end with (: ) 5. The statement return [expression] exits a function, optionally passing back an expression to the caller. A return statement with no arguments is the same as return None. Syntax def < functionname> ( < parameters >):

return [expression]

Function

VI

1.Example: def fun( ) : print( “ I am learning python”) fun ( )

# function definition # calling function

Output: I am learning python

2.Example: def print_hello( ): print('Hello!') print_hello( ) print('1234567') print_hello( ) output : Hello! 1234567 Hello! Note: The first two lines define the function. In the last three lines we call the function twice.

Function

VI

A programmer wants to find out the sum of numbers starting from 1 to 25 , 50 to 75 and 90 to 100 without function. Code: sum= 0 for i in range ( 1, 26 ): sum = sum +i print (“sum of integers from 1to 25 is:”, sum) sum= 0 for i in range ( 50, 76 ): sum = sum +i print (“sum of integers from 50 to 76 is:”, sum) sum= 0 for i in range ( 90, 101): sum = sum +i print (“sum of integers from 90 to 101 is:”, sum) Output: sum of integers from 1to 25 is: 325 sum of integers from 50 to 75 is: 1625 sum of integers from 90 to 100 is: 1045

Function

VI

A programmer wants to find out the sum of numbers starting from 1 to 25 , 50 to 75 and 90 to 100 with function. Code: def sum ( x, y ): s=0 for i in range ( x, y+1 ) s = s+ i print (‘ sum of integers from, ‘x’ to , ‘y’ is , s) sum ( 1,25 ) sum ( 50, 75) sum ( 90,100) Output: sum of integers from 1to 25 is: 325 sum of integers from 50 to 75 is: 1625 sum of integers from 90 to 100 is: 1045

Function

VI Example : x = 10 y=20 z=30

Example: x = 10 y=20 z=30

def add (a,b,c) : s = a+b+c return s print(add ( x,y,z))

def add (a,b,c): s = a+b+c return print(add ( x,y,z))

Output: 60

Output : None

Function

VI

Example : write a program to find the maximum of two numbers Code: def printMax ( num1, num2 ): print (“ num1 = “ , num1) print (“ num2 = “ , num1) if num1 > num2 : print ( “ The number”, num1, “ is greater than”, num2) elif num2 > num1: print ( “ The number”, num2, “ is greater than”, num1) else: print ( “ Both number”, num1, “ and”, num2, “ are equal”) printMax ( 20, 10 ) Output: num1 = 20 num2 = 10 The number 20 is greater than 10

Function

VI

Example : write a program to find factorial of numbers Code: def calc_ factorial ( num ): fact = 1 print (“ Entered number is :”, num) for i in range ( 1, num+1 ): fact = fact* i print ( “ factorial of number “ , num, “ is = “ ,fact ) number = int ( input ( “ Enter the number” )) calc_ factorial( number) Output: Entered number = 5 Entered number is : 5 factorial of number 5 is = 120

Function

VI

Recall that in mathematics the factorial of a number n is defined as n! = 1 ⋅ 2 ⋅ ... ⋅ n (as the product of all integer numbers from 1 to n). For example, 5! = 1 ⋅ 2 ⋅ 3 ⋅ 4 ⋅ 5 = 120. It is clear that factorial is easy to calculate, using a for loop. Imagine that we need in our program to calculate the factorial of various numbers several times (or in different places of code). Of course, you can write the calculation of the factorial once and then using Copy-Paste to insert it wherever you need it: Example: # compute 3! res = 1 for i in range(1, 4): res *= i print(res) Output: 6 Functions are the code sections which are isolated from the rest of the program and executed only when called. You've already met the function sqrt(), len() and print(). They all have something in common: they can take parameters (zero, one, or several of them), and they can return a value (although they may not return). For example, the function sqrt() accepts one parameter and returns a value (the square root of the given number). The print() function can take various number of arguments and returns nothing.

Function

VI

Now we want to show you how to write a function called factorial() which takes a single parameter — the number, and returns a value — the factorial of that number. Example: def factorial(n): res = 1 for i in range(1, n + 1): res *= i return res print(factorial(3)) Output: 6

Function

VI

Here's the function max( ) that accepts two numbers and returns the maximum of them (actually, this function has already become the part of Python syntax). Example: def max(a, b): if a > b: return a else: return b print(max(3, 5)) print(max(5, 3)) print(max(int(input()), int(input()))) Output: 5 5

Function

VI

Now you can write a function max3() that takes three numbers and returns the maximum of them. def max(a, b): if a > b: return a else: return b def max3(a, b, c): return max(max(a, b), c) print(max3(3, 5, 4)) Output: 5

Pass by Reference vs Value

VI

All parameters (arguments) in the Python language are passed by reference. It means if you change what a parameter refers to within a function, the change also reflects back in the calling function. # Function definition is here def changeme( mylist ): "This changes a passed list into this function“ print ("Values inside the function before change: ", mylist) mylist[2]=50 print ("Values inside the function after change: ", mylist) return # Now you can call changeme function mylist = [10,20,30] changeme( mylist ) print ("Values outside the function: ", mylist) Output Values inside the function before change: [10, 20, 30] Values inside the function after change: [10, 20, 50] Values outside the function: [10, 20, 50]

Function arguments

VI

You can call a function by using the following types of formal arguments − •Required arguments. •Keyword arguments. •Default arguments. •Variable-length arguments. • Required arguments. Required arguments are the arguments passed to a function in correct positional order. Here, the number of arguments in the function call should match exactly with the function definition.

# Function definition is here def printme( str ): "This prints a passed string into this function" print (str) # Now you can call printme function printme( )

Output it gives a syntax error To call the function printme(), you definitely need to pass one argument, otherwise it gives a syntax error .

Function arguments

VI

• Keyword Arguments Keyword arguments are related to the function calls. When you use keyword arguments in a function call, the caller identifies the arguments by the parameter name.

Note that the order of parameters does not matter.

# Function definition is here def printinfo( name, age ): "This prints a passed info into this function" print ("Name: ", name) print ("Age ", age) return # Now you can call printinfo function printinfo( age = 50, name = "miki" )

Output Name: miki Age 50

Function arguments – Keyword arguments

VI

# Function definition is here def printinfo( name, age ): "This prints a passed info into this function" print ("Name: ", name) print ("Age ", age) return # Now you can call printinfo function printinfo( age = "miki", name = 50 ) # Function definition is here def printinfo( name, age ): "This prints a passed info into this function" print ("Name: ", name) print ("Age ", age) return # Now you can call printinfo function printinfo(age = "miki", name = “50”)

Output Name: 50 Age miki

Output Name: 50 Age miki

Function arguments – Keyword arguments

VI

# Function definition is here def printinfo( name): "This prints a passed info into this function" print ("Name: ", name) print ("Age ", age) return # Now you can call printinfo function printinfo( age = 50 , name = "miki")

Output TypeError: printinfo() got an unexpected keyword argument 'age'

Function arguments

VI

• Default Argument A default argument is an argument that assumes a default value if a value is not provided in the function call for that argument.

# Function definition is here def printinfo( name, age = 35 ): "This prints a passed info into this function“ print ("Name: ", name) print ("Age ", age) return # Now you can call printinfo function printinfo( age = 50, name = "miki" ) printinfo( name = "miki" )

Output Name: miki Age 50 Name: miki Age 35

Function arguments- Default argument

VI def printinfo( name, age = 35 ):

"This prints a passed info into this function“ print ("Name: ", name) print ("Age ", age) return # Now you can call printinfo function printinfo( age = 50, name = "miki" ) printinfo( name = "miki“, age=67 ) def printinfo( name, age = 35 ): "This prints a passed info into this function“ print ("Name: ", name) print ("Age ", age) return printinfo( name = "miki") printinfo( name = "miki“, age=67 )

Output Name: miki Age 50 Name: miki Age 67

Output Name: miki Age 35 Name: miki Age 67

Function arguments- Default argument

VI

Example: def my_function(country = "Norway"): print("I am from " + country) my_function("Sweden") my_function("India") my_function() my_function("Brazil")

Output I am from Sweden I am from India I am from Norway I am from Brazil

Variable-length Arguments

VI

You may need to process a function for more arguments than you specified while defining the function. These arguments are called variable-length arguments and are not named in the function definition, unlike required and default arguments. An asterisk (*) is placed before the variable name that holds the values of all non keyword variable arguments.

def printinfo( arg1, *vartuple ): "This prints a variable passed arguments" print ("Output is: ") print (arg1) for var in vartuple: print (var) return # Now you can call printinfo function printinfo( 10 ) printinfo( 70, 60, 50 )

Output: Output is: 10 Output is: 70 60 50

Variable-length Arguments

VI def printinfo( *vartuple ): "This prints a variable passed arguments" print ("Output is: ") for var in vartuple: print (var) return # Now you can call printinfo function printinfo( 10 ) printinfo( 70, 60, 50 )

Output: Output is: 10 Output is: 70 60 50

Return Values

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The return statement is used to return a value from the function. Example: def my_function(x): return 5 * x print(my_function(3)) print(my_function(5)) print(my_function(9))

Output

15 25 45

The return Statement

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 You can return a value from a function as follows − Example : # Function definition is here def sum( arg1, arg2 ): # Add both the parameters and return them." total = arg1 + arg2 print( "Inside the function : ", total) return total # Now you can call sum function total = sum( 10, 20 ) print ("Outside the function : ", total) Output: Inside the function : 30 Outside the function : 30

Return Values

VI

Example: def minimum(a,b): if a
def minimum(a,b): if a < b: return a elif b < a: return b else: return " Both the number are equal" print(minimum(100,100))

Output

85

Output: Both the number are equal

Python Lambda / The Anonymous Functions

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A lambda function is a small anonymous function. A lambda function can take any number of arguments, but can only have one expression. Syntax: The syntax of lambda functions contains only a single statement

lambda arguments : expression Note: The expression is executed and the result is returned: Example A lambda function that adds 10 to the number passed in as an argument, and print the result: x = lambda a: a + 10 print(x(5)) Output: 15

Python Lambda / The Anonymous Functions

VI

Lambda functions can take any number of arguments: Example: A lambda function that multiplies argument a with argument b and print the result: x = lambda a, b: a * b print(x(5, 6)) Output: 30

Why Use Lambda Functions?

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The power of lambda is better shown when you use them as an anonymous function inside another function. Say you have a function definition that takes one argument, and that argument will be multiplied with an unknown number: def myfunc(n): return lambda a : a * n Use that function definition to make a function that always doubles the number you send in: def myfunc(n): return lambda a : a * n mydoubler = myfunc(2) print(mydoubler(11)) Output: 30

Why Use Lambda Functions?

VI

use the same function definition to make a function that always triples the number you send in: Example def myfunc(n): return lambda a : a * n mytripler = myfunc(3) print(mytripler(11)) Output: 33

Why Use Lambda Functions?

VI

use the same function definition to make both functions, in the same program: Example: def myfunc(n): return lambda a : a * n mydoubler = myfunc(2) mytripler = myfunc(3) print(mydoubler(11)) print(mytripler(11)) Output: 22 33

The Anonymous Functions/ Lambda function

VI These functions are called anonymous because they are not

declared in the standard manner by using the def keyword. You can use the lambda keyword to create small anonymous functions. Lambda forms can take any number of arguments but return just one value in the form of an expression. They cannot contain commands or multiple expressions. An anonymous function cannot be a direct call to print because lambda requires an expression Lambda functions have their own local namespace and cannot access variables other than those in their parameter list and those in the global namespace. Although it appears that lambda's are a one-line version of a function, they are not equivalent to inline statements in C or C++, whose purpose is by passing function stack allocation during invocation for performance reasons.

The Anonymous Functions

VI

Example:

# Function definition is here sum = lambda arg1, arg2: arg1 + arg2; # Now you can call sum as a function print ("Value of total : ", sum( 10, 20 )) print ("Value of total : ", sum( 20, 20 )) Output: Value of total : 30 Value of total : 40

Scope of Variables

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All variables in a program may not be accessible at all locations in that program. This depends on where you have declared a variable. The scope of a variable determines the portion of the program where you can access a particular identifier. There are two basic scopes of variables in Python − 1.Global variables 2. Local variables

Global vs. Local variables

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Variables that are defined inside a function body have a local scope, and those defined outside have a global scope. This means that local variables can be accessed only inside the function in which they are declared, whereas global variables can be accessed throughout the program body by all functions. When you call a function, the variables declared inside it are brought into scope. Example: total = 0; # This is global variable. # Function definition is here def sum( arg1, arg2 ): # Add both the parameters and return them." total = arg1 + arg2; # Here total is local variable. print ("Inside the function local total : ", total return total) # Now you can call sum function sum( 10, 20 ) (print "Outside the function global total : ", total) Output: Inside the function local total : 30 Outside the function global total : 0

Arguments

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We can pass values to functions. Example: def print_ hello(n): print('Hello ' * n) print() print_ hello(3) print_ hello(5) times = 2 print_ hello(times) output: Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Note : When we call the print _ hello function with the value 3, that value gets stored in the variable n. We can then refer to that variable n in our function’s code.

Arguments

VI

You can pass more than one value to a function Example: def multiple_print(string, n): print(string * n) print() multiple_print('Hello', 5) multiple_print('A', 10) Output: HelloHelloHelloHelloHello AAAAAAAAAA

Returning values

VI

We can write functions that perform calculations and return a result. Example 1: Here is a simple function that converts temperatures from Celsius to Fahrenheit. def convert (t): return t* 9/5+32 print (convert(20)) Output : 68.0 Note: The return statement is used to send the result of a function’s calculations back to the caller. Notice that the function itself does not do any printing. The printing is done outside of the function. That way, we can do math with the result, like below. print(convert(20)+5) If we had just printed the result in the function instead of returning it, the result would have been printed to the screen and forgotten about, and we would never be able to do anything with it

Default arguments and keyword arguments

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You can specify a default value for an argument. This makes it optional, and if the caller decides not to use it, then it takes the default value. Example: def multiple _ print(string, n=1): print(string * n) print() multiple _ print('Hello', 5) multiple _ print('Hello') Output: HelloHelloHelloHelloHello Hello

Note: Default arguments need to come at the end of the function definition, after all of the non-default arguments.