# If Else Statement

Decision making is about deciding the order of execution of statements based on certain conditions or repeat a group of statements until certain specified conditions are met.

The if statement in Python is used to perform operations on the basis of condition. By using if-else statement, you can perform an operation either the condition is true or false.

There are many ways to use if statement in Python:

1. If statement
2. If-else statement
3. Nested if Statement

## If Statement

The single if statement in Python is used to execute the code if the condition is true. The syntax of if statement is given below.

if expression:
statement

The expression is true, then 'statement' will be executed, otherwise 'statement' is skipped.

#### Example:

a=int(input("Enter value of a:"))
if a>10:
print ("value of a is greater than 10")
if a<10:
print ("value of a is less than 10")

#### Output:

Enter value of a:12
value of a is greater than 10

## If-else Statement

The if-else statement in Python is used to execute the code if condition is true or false. The syntax of if-else statement is given below.

if expression:
#statement-block1
else:
#statement-block2

If the 'expression' is true, the 'statement-block1' is executed, else 'statement-block1' is skipped and 'statement-block2' is executed.

#### Example:

a=int(input("Enter value of a:"))
if a>10:
print ("value of a is greater than 10")
else:
print ("value of a is less than 10")

#### Output:

Enter value of a:13
value of a is greater than 10

## elif statement

The elif statement enables us to check multiple conditions and execute the specific block of statements depending upon the true condition among them.

If expression1:
#statement-block1
elif expression2:
#statement-block2
elif expression3:
#statement-block3
else:
#statement-block4

If the 'expression' is true, the 'statement-block1' is executed, else if ‘expression2’ is true then 'statement-block2' is executed, else if ‘expression3’ is true then 'statement-block3' is executed otherwise 'statement-block4' is executed.

#### Example:

a=int(input("Enter value of a:"))
b=int(input("Enter value of b"))
if a>b:
print ("value of a is greater than b")
elif a<b:
print ("value of a is less than b")
else:
print ("a is equal to b" )

#### Ouput:

Enter value of a10
Enter value of b20
value of a is less than b

## Nested if

The syntax for a nested if statement is as follows.

if expression1:
statement-block1
if expression2:
statement-block2
else:
statement-block3
else:
statement-block4

#### Example:

a=int(input("Enter value of a:"))
if a<100:
if a>50:
print ("value of a is greater than 50")
else:
print ("value of a is less than 50")
else:
print ("value of a is greater than 100")

#### Output:

Enter value of a100
value of a is greater than 100

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