Python If-Else

What Is An If-Else Statement?

An if-else statement lets a program make a decision. The program checks a condition. If the condition is true, one block of code runs. If it is false, another block can run.

age = 18

if age >= 18:
    print("Adult")
else:
    print("Minor")

This prints Adult because the condition age >= 18 is true.

Conditions Produce Booleans

A condition is an expression that becomes either True or False.

score = 75
print(score >= 50)
print(score == 100)

Output:

True
False

Common comparison operators include:

• == equal to
• != not equal to
• > greater than
• < less than
• >= greater than or equal to
• <= less than or equal to

Use == for comparison. Use = for assignment.

Indentation Matters

Python uses indentation to know which lines belong inside the if, elif, or else block.

marks = 42

if marks >= 35:
    print("Pass")
    print("Keep practicing")
else:
    print("Try again")

Both indented print lines belong to the if block. If you remove the indentation, Python either changes the meaning or raises an error.

Using elif

Use elif when there are several possible cases.

marks = 82

if marks >= 90:
    grade = "A"
elif marks >= 75:
    grade = "B"
elif marks >= 60:
    grade = "C"
else:
    grade = "Needs practice"

print(grade)

Python checks from top to bottom and runs the first matching block.

Combining Conditions

Use and, or, and not to combine or reverse conditions.

age = 20
has_id = True

if age >= 18 and has_id:
    print("Allowed")

With and, both parts must be true. With or, at least one part must be true.

Common Mistakes

A common mistake is forgetting the colon.

if score >= 50
    print("Pass")

The correct version is:

if score >= 50:
    print("Pass")

Another mistake is writing else with a condition.

else score < 50:

Use elif for another condition, and use else as the final fallback.

Quick Summary

• if checks a condition.
• else runs when no earlier condition matched.
• elif checks another condition in the same decision chain.
• Conditions evaluate to True or False.
• Indentation defines the block.
• Use == to compare values and = to assign values.

Practice Quiz

Now practice this topic with MCQs and explanations:

Start the Python If-Else quiz