CODEWITHSUNDEEP
pythonpython-3.xpython-3.9
Peter Wensel
Peter Wensel

Reputation: 91

inspect.Parameter.annotation method returns a string for imported methods vs. a type when defined in scope

Consider the following python file test.py:

def accepts_string(s: str):
    pass

If I open a python shell, import this function and then grab the function's parameter s and its annotation I get a string literal.

>>> import inspect
>>> from test import accepts_string
>>> inspect.signature(accepts_string).parameters['s'].annotation
'str'

However, if I define the function in the shell - I get the expected results of an actual "class type".

>>> import inspect
>>> def accepts_string(s: str):
...    pass
...
>>> inspect.signature(accepts_string).parameters['s'].annotation
<class 'str'>

I would expect to always get the later results and I'm having trouble reconciling the different results based on whether the function is imported vs. defined live.

Upvotes: 3

Views: 1500

Answers (1)

Peter Wensel
Peter Wensel

Reputation: 91

This issue was due to a lack of understanding what from __future__ import annotations was doing. This was included at the top of my file and was omitted from the initial example I gave. Apologies for not realizing that when making this post.

As a user pointed out in the comments:

The future behavior will become the default behavior, it was supposed to in Python 3.10, but it got delayed, not sure the current status

I think I will need to use typing.get_type_hints anyway to reliably grab annotations for functions for future python versions.

Upvotes: 3

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