Pylint W0212 protected-access

Question

In Python, prefixing with one underscore indicates that a member should not be accessed outside of its class. This seems to be on a per-class basis like Java and C++.

However, pylint seems to enforce this convention on a per-object basis. Is there a way to allow per-class access without resorting to #pylint: disable=protected-access?

class A:
    def __init__(self):
        self._b = 5

    def __eq__(self, other):
        return self._b == other._b

Result:

pylint a.py
a.py:6: W0212(protected-access) Access to a protected member _b of a client class

Pylint describes the message here.

duck typing and __eq__ overloading can be dangerous. I recommend also testing self.__class__ == other.__class__ — gurney alex, Feb 29 '16 at 16:03
Related (but with Pycharm): https://stackoverflow.com/questions/42736044/python-access-to-a-protected-member-of-a-class — user202729, Oct 18 '18 at 09:58
See also [pylint issue #1802](https://github.com/PyCQA/pylint/issues/1802). — user202729, Oct 18 '18 at 10:02

Christian Geier · Accepted Answer · 2016-03-06T21:15:59.477

29

pylint doesn't know of which type other is (how should it, you can compare an instance of A to everything), therefore the warning. I don't think there is a way around disabling the warning.

You can disable the warning for only that one line with appending # pylint: disable=W0212 to that line.

edited Mar 06 '16 at 21:15

answered Feb 29 '16 at 14:18

Christian Geier

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Or `# pylint: disable=protected-access` – David Beauchemin Mar 26 '20 at 04:02
@DavidBeauchemin Is `pylint` able to perform introspection like `mypy`? The error in the example still issues for me even if I put `assert isinstance(other, A)` before the `return` statement. – adam.hendry Aug 31 '22 at 21:47

score 2 · Answer 2 · answered Aug 08 '19 at 15:14

Christian Geier is right about why you're getting the error, and how to disable it.

I'd encourage you to consider changing your code, though: pylint is telling you something important. From your example code looks like you want to use eq compare objects of class A to other objects of class A, but your example won't guarantee that a caller won't try A() == C(). Returning True when you check Circle()._radius == Sphere._radius seems likely to cause problems.

See this stackoverflow thread for discussion of how to handle this.

Pylint W0212 protected-access

2 Answers2

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