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math.copysign

representation

Return a value with the magnitude of x and the sign of y, including the sign of -0.0.

Syntax

math.copysign(...)

Its least obvious use is telling 0.0 from -0.0: comparison cannot do it, since -0.0 == 0.0 is True, but math.copysign(1, x) returns -1.0 precisely for negative zero. The sign is read straight from the sign bit, so it also works on nan and infinities, and the result is always a float even when both arguments are ints.

Examples

import math
print(math.copysign(3, -1))   # → -3.0
print(math.copysign(-3, 1))   # → 3.0
x = -12.5
print(math.copysign(1, x))   # → -1.0
print(math.copysign(2, -0.0))   # → -2.0

See also

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