Python If Else Elif Nested if in 5 Simple Steps

If, Elif, Else and Nested If:

In Python, we have 3 types of statements for decision-making – The Python if...elif...else statements

Elif is short for Else if, and it allows us to check multiple expressions. In case the current Elif returns False , the condition passes to the next elif, until any one of the elif returns True

If none of the Elif returns True, the statement in Else would be run

But, in case, if any of the if or elif returns True, the else statement will not be run.

Syntax:

if condition:
   statement1

elif condition:
   statement2

else:
   statement3

   

Working:

‘If’ Condition returned True:

The statement within the if (statement1) will be executed, and Python will not read elif and else statements

Output: statement1

‘Elif’ Condition returned True:

The statement within the if (statement1) will not be executed, and the condition passes to elif.

Since the elif condition returns True, statement2 will be executed.

Output: statement2

‘Else’ Condition returned True:

Python will not execute the statement within the if (statement1), and the condition passes to elif.

The elif condition now returns False, statement2 will not be executed.

Since If and Elif both returned False, the Else statement will be executed in no condition

Output: statement3

Example for If, Elif and Else Statements:

#Code to check whether num is a 2-Digit number or not

num= 14

if num<10:
   print("num is a 1-digit number ")

elif num>99:
   print("num is a 3-digit number ")

else:
   print("num is a 2-digit number ")

print("Since this is outside the if...elif...else statements, this will be executed all the time!")

When you run the program, the output will be:

num is a 2-digit number 
Since this is outside the if...elif...else statements, this will be executed all the time!

Nested If:

if condition-a:
   if condition-b:
      statement1

   elif condition-c:
      statement2

   else:
      statement3
else:
   statement4

Here, python reads lines 2-9, only if condition-a returns True

If condition-a was True, Python goes in and reads condition-b and so on.

If condition-a was False, then Python will not even read condition-b, condition-c and else.

This means that, even in any case either condition-b or condition-c returned True, since condition-a turns out to be False

In this case, else statement will be executed and the Program ends.

Example for Nested If:

#Here, we check if num is Positive, negative or Zero using Nested If

 num = int(input("Number: "))

 if num >= 0:
     if num == 0:
         print("Num is neither Positive nor Negative, Zero")
     else:
         print("Num is a Positive number")
 else:
     print("Num is a Negative number")

Output1:

Number: 10
Num is a Positive number

Output2:

Number: 0
Num is neither Positive nor Negative, Zero

Output3:

Number: -4
Num is a Negative number

Conclusion:

Now you must be having a clear idea on Python If Else Elif and Nested if Statements. If you are on your way to become a Pythonista, you might find our site really helpful. Hit this link for more python related posts
Check it out, it’s Simply the Best Code.