Why doesn't Python have a sign function?

Question

I can\'t understand why Python doesn\'t have a sign function. It has an abs builtin (which I consider sign\'s sister), but no si

Answer 1

numpy has a sign function, and gives you a bonus of other functions as well. So:

import numpy as np
x = np.sign(y)

Just be careful that the result is a numpy.float64:

>>> type(np.sign(1.0))

For things like json, this matters, as json does not know how to serialize numpy.float64 types. In that case, you could do:

float(np.sign(y))

to get a regular float.