Checking if something is callable or async callable in Python#

I wanted a mechanism to check if a given Python object was “callable” - could be called like a function - or “async callable” - could be called using await obj().

I ended up writing this helper function to help introspect objects and answer those questions:

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import asyncio
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import types
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from typing import NamedTuple, Any
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class CallableStatus(NamedTuple):
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    is_callable: bool
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    is_async_callable: bool
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def check_callable(obj: Any) -> CallableStatus:
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    if not callable(obj):
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        return CallableStatus(False, False)
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    if isinstance(obj, type):
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        # It's a class
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        return CallableStatus(True, False)
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    if isinstance(obj, types.FunctionType):
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        return CallableStatus(True, asyncio.iscoroutinefunction(obj))
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    if hasattr(obj, "__call__"):
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        return CallableStatus(True, asyncio.iscoroutinefunction(obj.__call__))
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    assert False, "obj {} is somehow callable with no __call__ method".format(repr(obj))

check_callable(obj) returns a CallableStatus named tuple, with an is_callable boolean saying if it can be caled and an is_async_callable boolean specifying if you need to use await with it.

I wrote these pytest tests to exercise the check_callable() function:

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import pytest
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class AsyncClass:
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    async def __call__(self):
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        pass
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class NotAsyncClass:
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    def __call__(self):
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        pass
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class ClassNoCall:
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    pass
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async def async_func():
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    pass
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def non_async_func():
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    pass
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@pytest.mark.parametrize(
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    "obj,expected_is_callable,expected_is_async_callable",
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    (
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        (async_func, True, True),
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        (non_async_func, True, False),
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        (AsyncClass(), True, True),
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        (NotAsyncClass(), True, False),
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        (ClassNoCall(), False, False),
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        (AsyncClass, True, False),
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        (NotAsyncClass, True, False),
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        (ClassNoCall, True, False),
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        ("", False, False),
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        (1, False, False),
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        (str, True, False),
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    ),
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)
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def test_check_callable(obj, expected_is_callable, expected_is_async_callable):
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    status = check_callable(obj)
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    assert status.is_callable == expected_is_callable
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    assert status.is_async_callable == expected_is_async_callable

See this commit for my initial implementation.

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Checking if something is callable or async callable in Python#

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