If, Elif, Else Conditions

Overview

Python's if/elif/else uses indentation (not braces) as block delimiters. The elif chain is Python's equivalent of else-if. Mastering conditional logic is the most fundamental skill in any programming interview.

Syntax

python

score = 85

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
elif score >= 60:
    grade = "D"
else:
    grade = "F"

print(f"Grade: {grade}")  # Grade: B

# One-liner ternary (conditional expression)
result = "pass" if score >= 60 else "fail"

Common Pitfalls

Python uses strict indentation (4 spaces) — mixing tabs and spaces causes IndentationError.
There is no 'switch' statement in Python < 3.10. Use if/elif chains or dicts for dispatch. Python 3.10+ has 'match/case'.
Interview tip: For multiple equality checks, prefer a dict dispatch table over long elif chains for cleaner, more extensible code.

Real-World Example

HTTP status code handler function

example

python

def handle_status(code: int) -> str:
    if 200 <= code < 300:
        return "Success"
    elif 300 <= code < 400:
        return "Redirect"
    elif 400 <= code < 500:
        return "Client Error"
    elif 500 <= code < 600:
        return "Server Error"
    else:
        return "Unknown status"

print(handle_status(404))  # Client Error
print(handle_status(200))  # Success

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