all Python 3Conditionalsconstruct

and, or, not

logic

The logical operators. and — both are true; or — at least one is true; not — negation. They short-circuit (lazy evaluation).

Syntax

a and b | a or b | not a

The non-obvious part: and and or return one of the operands, not True/False — "a or b" yields a when a is truthy, otherwise b, which is why "name or 'guest'" is the classic default-value idiom. Only not is guaranteed to give a clean bool.

Examples

print(True and False)  # → False
print(True or False)  # → True
print(not True)  # → False
age, has_id = 20, True
print(age >= 18 and has_id)  # → True
x = 5
print(x < 0 or x > 3)  # → True
print(1 < x < 10)  # → True (цепочка = неявный and)
name = "" or "Гость"
print(name)  # → Гость (короткое замыкание or)
val = None
safe = val and val.strip()  # → None (не вызывает ошибку из-за and)

See also

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