Question

I’m looking for a way to check for NaN values in Cython code. At the moment, I’m using:

if value != value:
    # value is NaN
else:
    # value is not NaN

Is there a better way to do this? Is it possible to use a function like Numpy’s isnan?

Answer 1

Taken from http://groups.google.com/group/cython-users/msg/1315dd0606389416, you could do this:

cdef extern from "math.h":
    bint isnan(double x)

Then you can just use isnan(value).

In newer versions of Cython, it is even easier:

from libc.math cimport isnan