Advice

I have a module (let's name it optional_module) that I want to be imported optionally, as it can be either present or absent. Now I do it this simple way:

try:
    import optional_module

except ImportError:
    ... # Working around the module

else:
    ... # Using the module

But mypy gives an error in case when optional_module is missing:

main.py:2: error: Cannot find implementation or library stub for module named
"optional_module"  [import-not-found]
        import optional_module
    ^
main.py:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

Yes, I looked at the link proposed by mypy, but it didn't help me to find the answer.

Of course, I could simply remove this check adding "# type: ignore" after the import line, but it would also suppress all useful checks of the module content in case when it does exist. So it's too rude.

Is there a more delicate and correct way to make mypy stop worrying and love my conditional import?

P.S. Here are my mypy configuration flags:

[mypy]
disallow_untyped_defs = True
check_untyped_defs = True
disallow_any_unimported = True
warn_return_any = True
warn_unreachable = True
warn_redundant_casts = True
warn_unused_ignores = True
pretty = True
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4 Replies 4

dROOOze
•

You say

but it would also suppress all useful checks of the module content in case when it does exist

but I can't reproduce this (see mypy Playground):

import math  # type: ignore[import-not-found]

reveal_type(math.pi)  # Revealed type is "builtins.float"
math.typo  # Module has no attribute "typo"  [attr-defined]
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Phant
•

Oops, you're right, thank you. I just assumed this behaviour of "#type: ignore" for some reason, and didn't even check it, shame on me. So, your answer has almost solved my problem. The only issue left is (in case of existing optional_module), mypy gives the following error:


main.py:2: error: Unused "type: ignore" comment  [unused-ignore]
        import optional_module # type: ignore[import-not-found]
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I see it's the result of enabled flag warn_unused_ignores in my config. I can just turn it off, but wouldn't like to do it globally. Is it possible to disable it just for my instance, without altering the global mypy INI file?

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dROOOze
•

Sure, import optional_module # type: ignore[import-not-found, unused-ignore]

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Phant
•

Yes, it works. Thank you, dROOOze

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