all Python 3mathterm

math.isinf

checking

Returns True if the number is infinite (float('inf') or float('-inf')).

Syntax

math.isinf(x)

Infinity almost never comes from dividing by zero — that raises ZeroDivisionError; the real sources are float('inf'), math.inf, parsing user input, and overflow in float arithmetic such as 1e308 * 10. If you only want to confirm a number is sane, reach for math.isfinite instead: isinf(nan) is False, so an infinity check alone is not enough.

Examples

import math
print(math.isinf(math.inf))   # → True
print(math.isinf(-math.inf))  # → True
print(math.isinf(42.0))       # → False
print(math.isinf(1e309))      # → True (overflow)
print(math.isinf(float('inf')))  # → True
print(math.isinf(0.0))  # → False

See also

Open in the full glossarydocs.python.orgReport an inaccuracy