Checked functions¶

@checked wraps sync and async callables and validates arguments before the function body runs. It also validates return values unless you disable return checking.

ensure(value, annotation) is the inline validation helper. It returns the original value after checking it.

Checks can be disabled with DEPEND_DISABLE_CHECKS=1.

Example¶

from depend import ValidationError, checked, ensure, refined

PositiveInt = refined(int, lambda x: x > 0, name="PositiveInt")

@checked
def repeat(text: str, n: PositiveInt) -> str:
    return text * n

@checked
def broken(n: PositiveInt) -> PositiveInt:
    return -n

assert repeat("ha", ensure(3, PositiveInt)) == "hahaha"

try:
    repeat("ha", -1)
except ValidationError:
    pass