all Python 3Conditionalsconstruct

if-else

branching

A two-branch conditional. If the condition is true the if block runs, otherwise the else block.

Syntax

if условие:
    блок1
else:
    блок2

When both branches just assign to one variable, the ternary conditional expression "A if condition else B" is tighter — the same choice in one line instead of a four-line if-else. Keep the full if-else for branches that do several things.

Examples

x = -3
if x >= 0:
    print("неотрицательное")
else:
    print("отрицательное")  # → отрицательное

n = 7
if n % 2 == 0:
    print("чётное")
else:
    print("нечётное")  # → нечётное

s = ""
if s:
    print("не пусто")
else:
    print("пусто")  # → пусто — пустая строка ложна

# Однострочная форма — условное выражение
val = None
result = val if val is not None else 0
print(result)  # → 0

See also

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