Is IntelliJ Python 3 inspection "Expected a dictionary, got a dict" a false positive for super with **kwargs?

Question

I use Python 3 and want to wrap argparse.ArgumentParser with a custom class that sets
formatter_class=argparse.RawDescriptionHelpFormatter by default. I can do this successfully, however IntelliJ IDEA 2017.1 with Python Plugin (PyCharm) gives a warning for the following code:

class CustomParser(argparse.ArgumentParser):
def __init__(self, formatter_class=argparse.RawDescriptionHelpFormatter, **kwargs):
    # noinspection PyArgumentList
    super().__init__(formatter_class=formatter_class, **kwargs)  # warning in this line for the last argument if suppression comment above removed

If one removes the comment with the IntelliJ suppression command the warning on kwargs is “Expected a dictionary, got a dict”, however it is working. Is this a false positive warning or can this be done better without the warning? Is there a real issue behind this warning that it helps avoiding?

Side question: Is there a difference in using
formatter_class = kwargs.pop('formatter_class', argparse.RawDescriptionHelpFormatter) instead of explicitly defining the named parameter in the signature? According to PEP20 more explicit in the signature is better, right?

Asked By: jan

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Source

Answer 1

Yes, that appears to be a false positive.

You asked about formatter_class=kwargs.pop('formatter_class', argparse.RawDescriptionHelpFormatter). Please don’t do that. Mutating kwargs, which appears as the next argument, seems Bad. Additionally, default keyword args should be set to a simple constant rather than some mutable datastructure, as there is a big difference between evaluating at import time and evaluating at run time. See e.g. http://www.effbot.org/zone/default-values.htm . The usual idiom would be formatter_class=None in the signature, and then in the body you test for None and you mutate kwargs to your heart’s content.

Answered By: J_H

Answer 2

Marking all the virtual environment directories stored inside the project (e.g. ./venv) as excluded has solved it for me with PyCharm 2020.2.3.

To do so: right-click on the virtual environment directories in the project tree and select: Mark Directory as -> Excluded. Solution from https://youtrack.jetbrains.com/issue/PY-39715.

Answered By: Remi Cuingnet

Answer 3

Yes, that appears to be a false positive. As said @J_H

The best descicion i got by Chat-gpt. It was
adding comment # type: ignore at the end of string

class Price(ItemBase):
def __init__(self, *args, **kwargs):
    super(Price, self).__init__(*args, **kwargs)  # type: ignore

Answered By: Sergey Grunenko

Is IntelliJ Python 3 inspection "Expected a dictionary, got a dict" a false positive for super with **kwargs?

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