if, elif, and else

Now that you can produce booleans, you can make your program decide. An if statement runs a block of code only when a condition is true. Add elif and else and your program can choose between many paths.

What You'll Learn

• The if statement and Python's indentation
• Adding elif and else branches
• Putting conditions in the right order
• The one-line ternary expression

The if Statement

Two things to notice: the line ends with a colon :, and the code inside is indented with 4 spaces. Python uses that indentation (not braces) to know what belongs inside the if.

if / else

else runs when the condition is false:

if / elif / else

Use elif (short for "else if") to test more conditions in order. Only the first true branch runs:

Order Matters

Because only the first true branch runs, put the most specific conditions first. This diagram shows how a value flows through the checks:

If you checked x > 10 first, a value like 25 would stop there and never reach x > 20.

The Ternary Expression

For a simple either/or choice, you can pick a value in one line:

Key Takeaways

• if condition: runs indented code when the condition is true
• Python uses 4-space indentation to mark blocks
• elif adds more conditions; else is the fallback
• Only the first true branch runs, so order matters
• Ternary: value_if_true if condition else value_if_false