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math.fmod

remainder

The C-library fmod remainder: the sign matches x (differs from %).

Syntax

math.fmod(...)

The difference from % is not cosmetic: fmod follows C and takes the sign of the dividend, while % takes the sign of the divisor, so math.fmod(-10, 3) is -1.0 whereas -10 % 3 is 2. Use % for integers and fmod for floats — fmod is exact by construction, while % loses accuracy when the operands differ wildly in magnitude. The result is always a float, and a zero divisor raises ValueError, not ZeroDivisionError.

Examples

import math
print(math.fmod(10, 3))   # → 1.0
print(math.fmod(-10, 3))   # → -1.0
print(-10 % 3)   # → 2
print(math.fmod(10, -3))   # → 1.0
print(math.fmod(7.5, 2))   # → 1.5
print(math.fmod(10, 0))   # → ValueError

See also

Common errors

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