sqrt raises AttributeError on unexpected input

[silvioricardoc]

>>> numpy.sqrt(9)
3.0
>>> numpy.sqrt(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: sqrt

I expected a TypeError or ValueError, and spent quite some time trying to understand why sqrt was "missing"...

[charris]

None is treated as an object, which is why a sqrt attribute is looked for. Perhaps the error/error_message can be improved.

[timhoffm]

Same problem with sympy integers:

>>> import numpy as np
>>> x = Integer(10)
>>> np.sqrt(x)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Integer' object has no attribute 'sqrt'

Reported in matplotlib/matplotlib#13106.

A better error message would really help to find out what's going on.

[eric-wieser]

+1 from me on improving the error message. Raising TypeError("Object loop of ufunc {} does not support object of type {} which has no {} method") if the attribute is absent would be helpful.

I'm not sure if we should also try and check is the attribute is callable.

Perhaps chaining the exception would be useful here