Python If...Else

Python If...Else: Conditional Branching and Guard Clauses

Python if, elif, and else statements control which block of code runs based on boolean conditions. Python evaluates branches from top to bottom and executes only the first branch whose condition is True.

Clean conditionals keep nesting shallow. When you check edge cases early with guard clauses, the main logic stays readable at the top indentation level.

Standard if / elif / else and Ternary Expressions

Use elif (short for "else if") for mutually exclusive branches, and use a single-line ternary expression only for short value selection.

http_status = 429

if http_status == 200:
    outcome = "Success"
elif http_status == 429:
    outcome = "Rate limited, retry later"
elif http_status >= 500:
    outcome = "Server error"
else:
    outcome = "Client request error"

# Short inline ternary expression
badge = "OK" if http_status < 400 else "Alert"
print(outcome, badge)

Chained Comparisons

Python lets you chain comparison operators just like math notation:

age = 24
if 18 <= age <= 65:
    print("Eligible age range")

Common Mistakes to Avoid

• Writing multiple if statements instead of elif: Separate if blocks all run independently, which can trigger overlapping branches.
• Using = instead of == in conditions: Python flags if x = 5: as a SyntaxError, protecting you from accidental assignment.
• Deeply nested if ladders: Return early inside functions (if not user: return None) instead of wrapping the entire body inside an if block.

Frequently Asked Questions

Does Python have a switch statement?

Python 3.10 added match ... case structural pattern matching, which handles both simple constant switching and complex object patterns cleanly.

How do I write an empty if branch temporarily?

Place the pass statement inside the indented block so Python parses valid syntax while you finish writing the logic.

When should I avoid ternary expressions?

Avoid nesting one x if cond else y inside another. Multi-line if / else blocks are far easier to read and debug.