python isinf

The `isinf()` function in Python is used to check if a given number is infinity. It returns `True` if the number is positive or negative infinity, and `False` otherwise.

Here's an example:

import math

print(math.isinf(10))        # False
print(math.isinf(float('inf')))   # True
print(math.isinf(float('-inf')))  # True

In the above code, `math.isinf()` is used to check if a number is infinity or not. The first print statement returns `False` because 10 is not infinity. The second and third print statements return `True` because `float('inf')` and `float('-inf')` represent positive and negative infinity, respectively.