Conditional Statements in Python: If, If else, Elif, Nested if Statements

We tend to make a lot of decisions in our life whether it is related to work or personal life. We usually make decisions based on few conditions, like I will buy a car if I get an increment next year.

Conditions are very important to everyone’s life to have a pleasant experience in our career or lifestyle. Similarly, In Programming languages also conditions play a pivotal role. They are the ones that help us develop a code that can satisfy all the business conditions and perform well.

Usually in Python Programming Language code executes in a sequential manner like the first line will be executed first followed by second line and so on until the end of the code. Conditional statements come into picture when we must decide that a certain part of code should run only if the condition is True.

In this article we will have a look into the different types of conditional statements that are present in Python Programming Language along with the Syntax of each statement, code and output examples.

If Statement

If statement is used when we must execute a code block only if a given test condition is True. First the program will evaluate the test conditional expression and will only execute the code block if the test conditional expression is True. IF statement is written by using the if keyword.

Syntax

If test condition expression:

         Statement 1

         Statement 2…….

Example

# Example for IF Statement

# When Condition is True

number = 6

if number > 0:

         print (number,”Positive Number”)

print (“Outside If block”)

# When Condition is False

number = -6

if number > 0:

         print (number,”Positive Number”)

print (“Outside If block”)

Output

6 Positive Number

Outside If block

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If Else Statement

We cannot use only If statements for all the conditions that are required in each problem statement to develop our code. In some situations, we might have multiple conditions, that is why we have another conditional statement called IF ELSE.

This is like an IF statement, but we have two blocks here and one conditional expression. The if code block will run if the expression is True and else code block will run if the expression is false. IF ELSE statement uses if and else keywords.

Syntax

If test condition expression:

         Code block for if

Else:

         Code block for else

Code block outside

Example

# Example for IF ELSE Statement

# When Condition in True

number = 6

if number > 0:

         print(number,”Positive Number”)

else:

         print(number,”Negative Number”)

print(“Outside If block”)

# When Condition in True

number = -1

if number > 0:

         print(number,”Positive Number”)

else:

         print(number,”Negative Number”)

print(“Outside If block”)

Output

6 Positive Number

Outside If block

-1 Negative Number

Outside If block

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Elif Statement

As discussed in the above conditional statement we tend to have multiple conditions that we need to take care of when we are developing a code for a business-related problem. One of such statements is ELIF Statement, this is used when we must check multiple conditions.

ELIF is a short form for ELSE IF. In ELIF, first the test condition expression is checked if it is True then the if code block is executed. If the ELIF first condition is false, the next ELIF test condition is checked and this is repeated until the last elif condition. If all the ELIF conditions are false, then the else code block will be executed. ELIF Statements are written by using if elif and else keywords.

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Syntax

If test condition expression:

         Code block for if

elif test condition expression 1:

         Code block for elif 1

elif test condition expression 2:

         Code block for elif 2

….

else:

         Code block for else

Code block outside

Example

# Example for ELIF Statement

# When one of the Condition is True

number = 90

if number == 0:

         print(number,”Condition 1 is true”)

elif number == 30:

         print(number,”Condition 2 is true”)

elif number == 60:

         print(number,”Condition 3 is true”)

elif number == 90:

         print(number,”Condition 4 is true”)

else:

         print(number,”None of the Conditions are true”)

print(“Outside elif block”)

# When none of the Conditions are True

number = 50

if number == 0:

         print(number,”Condition 1 is true”)

elif number == 30:

         print(number,”Condition 2 is true”)

elif number == 60:

         print(number,”Condition 3 is true”)

elif number == 90:

         print(number,”Condition 4 is true”)

else:

         print(number,”None of the Conditions are true”)

print(“Outside elif block”)

Output

90 Condition 4 is true

Outside elif block

50 None of the Conditions are true

Outside elif block

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Nested IF Statement

Nested IF Statements are used when we want to execute a certain code where there are two or more conditions to be met. This statement uses only if and else keywords.

Syntax

If test condition expression:

     If test condition expression:

                     Code block for if

         else:

                     code block for else

else:

code block for else

Example

# Example for NESTED IF Statement

# Both the conditions are true

number = 10

if number >= 0:

         if number == 10:

                     print(‘The given number is 10’)

         else:

                     print(“The given number is a positive number”)

else:

         print(“The given number is a negative number”)

print(“Outside nested if block”)

# One of the conditions are true

number = 20

if number >= 0:

         if number == 10:

                     print(‘The given number is 10’)

         else:

                     print(“The given number is a positive number”)

else:

         print(“The given number is a negative number”)

print(“Outside nested if block”)

## None of the conditions are true

number = -10

if number >= 0:

         if number == 10:

                     print(‘The given number is 10’)

         else:

                     print(“The given number is a positive number”)

else:

         print(“The given number is a negative number”)

print(“Outside nested if block”)

Output

The given number is 10

Outside nested if block

The given number is a positive number

Outside nested if block

The given number is a negative number

Outside nested if block

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Conclusion

In this article we got to know the importance of the conditional statements in the Programming language. We deep dived into the different conditional statements in Python Programming language. We have also looked into the practical implementation of the various conditional statements along with their suitable examples.

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