Conditional Statements in Python

What is use of conditional statements: 

Conditional statements are used to compare two or more than two variables and then make decisions. These statements are used in decision making operations.

Following are conditional statements in Python ,

1.    if Statements:

if statement is used in Python for decision making.

Syntax: 

            if test expression:

               statement(s)  

  

here compiler evaluates the expression only if condition becomes true.

if condition becomes false then statements will not get execute.

For Example:

1. num=100 

if num> 101:

    print(num,"Number is positive")

OutPut:

10 Number is positive

2. num=20

if num%2!=0:

    print(num,"Is odd number")

O/P: will not display any thing because condition becomes false.

2.    if-else block

Syntax: 

          if test expression:

        body of if

          else:

          body of else 

*  if-else statement evaluates test expression and execute the body of if only when condition becomes true.

*  the body of else block will get execute when condition becomes false.

# Program to display number is odd or even

print("Demonstration of if-else statement")

num=11 

if num%2==0:

    print(num,"is even")

else:

        print(num,"is odd")

o/p: Demonstration of if-else statement

11 is odd

# Program to display number is odd or even take user input

print("Demonstration of if-else statement")

num=int(input("Enter any number"))

if num%2==0:

    print (num,"is even")

else:

        print(num,"is odd")

o/p:

Demonstration of if-else statement

Enter any number23

23 is odd

# leap year or not

year=int(input("Enter year"))

if year%4==0:

    print(year,"Year is leap")

else:

    print(year,"Year is not leap")

o/p:

Enter year2020

2020 Year is leap

# Check count of odd and even numbers in list

list1=[2,10,3,4]

even, odd=0,0

for num in list1:

    if num%2==0:

        even+=1 

    

else:

    odd+=1 

    print("lList elemets are", list1)

    print("The list of even numbers in list",even)

    print("The list of odd numbers in list",odd)

    

o/p:

lList elemets are [2, 10, 3, 4]

The list of even numbers in list 3

The list of odd numbers in list 1

3.    if- elif-else

Syntax:

        

          if test condition:

          body of if

           elif test expression:

           body of elif

          else:

          body of else

The elif is short for else-if.

It helps to check multiple expression.

If the condition for if is false then compiler will check elif block for next condition

and so on

If all condition becomes false the body of else block will get executed.

Only one block among several block get executed according to the condition

The if block can have only one else block but can have multiple elif blocks.

# Demonstration of if-elif-else statements

num=int(input("Enter number"))

if num>0:

    print(num," is positive")

elif num==0:

        print(num,"is zero")

else:

    print(num,"Negative number")

o/p:

Enter number1

1 is positive

# number is smaller,bigger or equal

num1=int(input("Enter Number"))

num2=int(input("Enter second number"))

if num1>num2:

    print(num1,"is bigger")

elif num1<num2:

    print(num2,"is bigger")

else:

    print(num1,num2," are equal")

o/p:

Enter Number12

Enter second number12

12 12 are equal

4.    Nested If Statement

Syntax:

         if test expression: 

         statement

         if test expression:

         statement

         else:

         statement

         else:

         statement

* You can have if statements inside the if statements.this is called nested if statement.