if — Intermediate Examples
Starts a conditional statement; executes block only if condition is true
Conditional expressions (ternary)
One-line if/else for concise assignments.
python
# Ternary expression x = 42 label = "even" if x % 2 == 0 else "odd" print(f"{x} is {label}") # Nested ternary (use sparingly) score = 85 grade = "A" if score >= 90 else "B" if score >= 80 else "C" if score >= 70 else "F" print(f"Score {score}: Grade {grade}") # In list comprehensions nums = range(1, 11) labels = [f"{n}: {'even' if n % 2 == 0 else 'odd'}" for n in nums] print(labels[:4])
The ternary expression 'x if condition else y' is useful in assignments and comprehensions. Avoid nesting more than one level.
Short-circuit evaluation
How 'and' and 'or' work with if.
python
# 'and' returns first falsy or last value print(1 and 2 and 3) print(1 and 0 and 3) # 'or' returns first truthy or last value print(0 or "" or "fallback") print("first" or "second") # Practical: safe dictionary access config = {} debug = config.get("debug") or False print(f"Debug: {debug}") # Guard pattern items = [1, 2, 3] if items and items[0] > 0: print("First item is positive")
Python short-circuits: 'and' stops at the first falsy value, 'or' stops at the first truthy value. The guard pattern 'if items and items[0]' prevents IndexError on empty lists.
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