CODEWITHSUNDEEP
pythonwindowscross-platformmypy
ChrisB
ChrisB

Reputation: 3724

Prevent mypy errors in platform dependent python code

I have something akin to the following piece of python code:

import platform
if platform.system() == "Windows":
    import winreg
    import win32api

def do_cross_platform_thing() -> None:
    if platform.system() == "Windows":
        # do some overly complicated windows specific thing with winreg and win32api
    else:
        # do something reasonable for everyone else

Now, on linux, mypy complains that

Is there any reasonable way to deal with this ? My current solution is

Are there any better solutions for this?

Upvotes: 4

Views: 571

Answers (2)

Niko Fohr
Niko Fohr

Reputation: 33920

You may use the

# type: ignore[some-mypy-code,unused-ignore]

syntax introduced in Mypy 1.4 (Released 2023-06-20, PR 15164). Replace the some-mypy-code with the error code which you get from mypy. Example taken from the PR:

try:
    import graphlib  # type: ignore[import,unused-ignore]
except ImportError:
    pass

In the above, the ignore[import] ignores the import error (on Python 3.7 for example, where graphlib does not exist) and ignore[unused-ignore] ignores the error caused by the warn_unused_ignores mypy setting on e.g. Python 3.9 where this module is available.

Upvotes: 2

ChrisB
ChrisB

Reputation: 3724

Ok, after checking the Docs as @SUTerliakov so kindly suggested, it seems that i have to change my

if platform.system() == "Windows"

to this, semantically identical check:

if sys.platform == "win32"

Only this second version triggers some magic builtin mypy special case that identifies this as a platform check and ignores the branch not applicable to its plattform.

Upvotes: 4

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