Python: How to check if an imported module/package/class is from standard library

Question

Is there a possibility to verify if an import comes from the standard library or not?

For example:

from math import sin #from the standard library.
from my_module import MyClass #not from the standard library.

Asked By: Jon

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Source

Answer 1

There is no simple way to do this, as the Python standard library is not implemented in a special way – to Python, there is no distinction between the standard library and other modules.

At best, you could use the inspect module to try and find some indicators, for example, using inspect.getsourcefile() to find where the source file is located, then using that to check if it’s a core library. This won’t work particularly well, however, as any modules in C will return a TypeError as they are builtins – but you can’t presume they are from the standard library, as any C extension module will do the same thing.

If you really have to do this, my suggestion would be to keep a list of standard library module names and do it that way – it’s not a great solution, but it’s likely to be more stable than any alternative.

Answered By: Gareth Latty

Answer 2

If you keep your own modules in a specific directory, you could do something looking at the module’s __file__ property:

>>> import os
>>> os.__file__
'/usr/lib64/python2.6/os.pyc'

>>> import my_module
>>> my_module.__file__
'/path/to/my_packages/.../my_module.pyc'

Answered By: E.Z.

Answer 3

Below source code will tell you whether a module a standard Python module or not

def is_standard_module(module_name):
    if module_name in sys.builtin_module_names:
        return True
    installation_path = None
    try:
        installation_path = importlib.import_module(module_name).__file__
    except ImportError:
        return False
    linux_os, _, _ = platform.linux_distribution()
    return "dist-packages" not in installation_path if linux_os == "Ubuntu" else "site-packages" not in installation_path

Answered By: Mohyt

Answer 4

In python 3.10+, you can use sys.stdlib_module_names

import sys
import types

def is_stdlib(module: str | types.ModuleType) -> bool:
    """
    Return True if module is in stdlib
    """

    if isinstance(module, str):
        return module.split('.')[0] in sys.stdlib_module_names

    if isinstance(module, types.ModuleType):
        return module.__name__.split('.')[0] in sys.stdlib_module_names

    raise TypeError('module must be a string or module object')

Answered By: aviso

Python: How to check if an imported module/package/class is from standard library

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