Nose tools and pylint

Question

What is the right way to use nose.tools and keep pylint happy?

The following code:

'''
This is a test
'''

import nose.tools
import nose.tools.trivial

nose.tools.assert_equal(1, 1)
nose.tools.assert_equals(1, 1)

nose.tools.trivial.assert_equal(1, 1)
nose.tools.trivial.assert_equals(1, 1)

Results in the following pylint errors:

$ pylint -i y -r n /tmp/aseq.py
************* Module aseq
E1101:  8,0: Module 'nose.tools' has no 'assert_equal' member
E1101:  9,0: Module 'nose.tools' has no 'assert_equals' member
E1101: 11,0: Module 'nose.tools.trivial' has no 'assert_equal' member
E1101: 12,0: Module 'nose.tools.trivial' has no 'assert_equals' member

Of course, one could disable E1101, is there a cleaner way?

Answer 1

Instead of disabling E1101, you should put:

ignored-classes=nose.tools,nose.tools.trivial

in .pylintrc, under the [TYPECHECK] section.

As it stands in the pylint doc, this option is "useful for classes with attributes dynamically set".

Answer 2

nose.tools.trivial simply inspects unittest.TestCase class on the fly and makes all "public" methods starting from assert available from nose.tools or nose.tools.trivial:

nose/tools/__init__.py:

from nose.tools.nontrivial import *
from nose.tools.nontrivial import __all__ as nontrivial_all
from nose.tools.trivial import *
from nose.tools.trivial import __all__ as trivial_all

__all__ = trivial_all + nontrivial_all

nose/tools/trivial.py:

...

class Dummy(unittest.TestCase):
    def nop():
        pass
_t = Dummy('nop')

for at in [ at for at in dir(_t)
            if at.startswith('assert') and not '_' in at ]:
    pepd = pep8(at)
    vars()[pepd] = getattr(_t, at)
    __all__.append(pepd)

...

Pylint cannot handle this "hacky" behavior.

Consider using nose.tools.eq_ instead of assert_equal and assert_equals (these methods are actually the same). Hope that helps.

Answer 3

Pylint doesn't understand nose underlying magic. As suggested, solutions include disabling E1101 or ignoring related classes. But the best is to contribute to the pylint-brain project by submitting there a simple description of the part of the API not grasped by Pylint. This should be pretty simple from the doc and example you'll find there.