numpy.ma.masked_where() return object not recognized as numpy.ma.MaskedArray

[yumasheta]

Steps to reproduce

Consider this short python script:

"""Quick test to show pylint error."""

import numpy as np

DATA = np.array([1, 2, 3])
DATA = np.ma.masked_where([1, 0, 0], DATA)
print(DATA.mask)
assert isinstance(DATA, np.ma.MaskedArray)

DATA = np.ma.array([1, 2, 3], mask=[1, 0, 0])
print(DATA.mask)
assert isinstance(DATA, np.ma.MaskedArray)

With output:

[ True False False]
[ True False False]

Running pylint on that code returns:

7:6: E1101: Instance of 'ndarray' has no 'mask' member (no-member)

Current behavior

The object returned by numpy.ma.masked_where() is an instance of numpy.ma.MaskedArray, just as the object returned by numpy.ma.array() is. However, pylint does not recognize the return value of numpy.ma.masked_where() as such.

Expected behavior

Pylint should recognize that numpy.ma.masked_where() returns a numpy.ma.MaskedArray.

pylint --version output

pylint 2.4.4
astroid 2.3.3
Python 3.8.1 (default, Dec 21 2019, 20:57:38) 
[GCC 9.2.0]

[hippo91]

@yumasheta thanks for this bug report. I'll investigate ASAP.

[hippo91]

@yumasheta the problem comes from the fact that there is not a brain for numpy.ma module in astroid yet. I put it on my todo list but i'm really busy right now so it will take a long time before seeing it in astroid.
Feel free to add it through a PR. I'll be happy to help you if needed.

[hippo91]

@yumasheta this bug should be fixed once pylint-dev/astroid#1148 will be merged and by authorizing pylint to dynamically load numpy with --extension-pkg-allow-list=numpy option.
If however you don't want to authorize this loading, then an improvement of astroid's numpy brain is required but may take a very long time to be set up.

[hippo91]

I'm reopening the issue because what was made in pylint-dev/astroid#1148 was not wise.

[hippo91]

The problem will be fixed definitively through an update of astroid numpy brain modules.