Reference · Math

math.isinf

math.isinf(num) -> bool

What it does

Whether a number is positive or negative infinity, as Python's math.isinf. An int is never infinite. A float becomes infinite when arithmetic runs past the largest float, or when it is made so with float("inf").

Examples

print(math.isinf(float("inf")), math.isinf(float("-inf")), math.isinf(1))print(math.isinf(1e308 * 10), 1e308 * 10)

true true falsetrue inf

Edge cases

• NaN is not infinite: math.isinf(nan) is false, as math.isfinite(nan) is. Test for it with math.isnan.
• The largest float, 1.8e308, is not infinite; 1e309 as a literal already is.
• Division by zero does not make infinity: it is a runtime error, so math.isinf never sees it.

print(math.isinf(float("nan")), math.isinf(1.8e308), math.isinf(1e309))

false true true

Errors

An argument that is not a number is a runtime error, not an error value.

print(math.isinf("inf"))

line 1: `math.isinf` expects a number as argument 1, got str

Chaining

In a pipeline the number comes first:

print(1e308 * 10 | math.isinf)print([1.0, float("inf"), 3.0] | map(math.isinf))

true[false, true, false]

See also

math.isfinite, math.isnan, float

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