Import a python module without the .py extension

Here is a solution for Python 3.4+:

from importlib.util import spec_from_loader, module_from_spec
from importlib.machinery import SourceFileLoader 

spec = spec_from_loader("foobar", SourceFileLoader("foobar", "/path/to/foobar"))
foobar = module_from_spec(spec)
spec.loader.exec_module(foobar)

Using spec_from_loader and explicitly specifying a SourceFileLoader will force the machinery to load the file as source, without trying to figure out the type of the file from the extension. This means that you can load the file even though it is not listed in importlib.machinery.SOURCE_SUFFIXES.

If you want to keep importing the file by name after the first load, add the module to sys.modules:

sys.modules['foobar'] = foobar

You can find an implementation of this function in a utility library I maintain called haggis. haggis.load.load_module has options for adding the module to sys.modules, setting a custom name, and injecting variables into the namespace for the code to use.

Like others have mentioned, you could use imp.load_source, but it will make your code more difficult to read. I would really only recommend it if you need to import modules whose names or paths aren't known until run-time.

What is your reason for not wanting to use the .py extension? The most common case for not wanting to use the .py extension, is because the python script is also run as an executable, but you still want other modules to be able to import it. If this is the case, it might be beneficial to move functionality into a .py file with a similar name, and then use foobar as a wrapper.

imp.load_source(module_name, path) should do or you can do the more verbose imp.load_module(module_name, file_handle, ...) route if you have a file handle instead

importlib helper function

Here is a convenient, ready-to-use helper to replace imp, with an example, based on what was mentioned at: https://stackoverflow.com/a/43602645/895245

main.py

#!/usr/bin/env python3

import os
import importlib
import sys

def import_path(path):
    module_name = os.path.basename(path).replace('-', '_')
    spec = importlib.util.spec_from_loader(
        module_name,
        importlib.machinery.SourceFileLoader(module_name, path)
    )
    module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(module)
    sys.modules[module_name] = module
    return module

notmain = import_path('not-main')
print(notmain)
print(notmain.x)

not-main

x = 1

Run:

python3 main.py

Output:

<module 'not_main' from 'not-main'>
1

I replace - with _ because my importable Python executables without extension have hyphens. This is not mandatory, but produces better module names.

This pattern is also mentioned in the docs at: https://docs.python.org/3.7/library/importlib.html#importing-a-source-file-directly

I ended up moving to it because after updating to Python 3.7, import imp prints:

DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses

and I don't know how to turn that off, this was asked at:

• The imp module is deprecated
• How to ignore deprecation warnings in Python

Tested in Python 3.7.3.

If you install the script with package manager (deb or alike) another option would be to use setuptools:

"...there’s no easy way to have a script’s filename match local conventions on both Windows and POSIX platforms. For another, you often have to create a separate file just for the “main” script, when your actual “main” is a function in a module somewhere... setuptools fixes all of these problems by automatically generating scripts for you with the correct extension, and on Windows it will even create an .exe file..."

https://pythonhosted.org/setuptools/setuptools.html#automatic-script-creation

While the importlib answer is the correct way to do it, I was looking for something more concise.

You can use the runpy module, with the following caveat (emphasis mine, links removed):

Furthermore, any functions and classes defined by the executed code are not guaranteed to work correctly after a runpy function has returned. If that limitation is not acceptable for a given use case, importlib is likely to be a more suitable choice than this module.

Having said that, as of Python 3.11, the following works perfectly:

import runpy
import types

my_module = types.SimpleNamespace(**runpy.run_path("/path/to/file"))

import imp has been deprecated.

The following is clean and minimal for me:

import sys
import types
import  pathlib

def importFileAs(
        modAsName: str,
        importedFilePath: typing.Union[str,  pathlib.Path],
) -> types.ModuleType:
    """ Import importedFilePath as modAsName, return imported module
by loading importedFilePath and registering modAsName in sys.modules.
importedFilePath can be any file and does not have to be a .py file. modAsName should be python valid.
Raises ImportError: If the file cannot be imported or any Exception: occuring during loading.

Refs:
Similar to: https://stackoverflow.com/questions/19009932/import-arbitrary-python-source-file-python-3-3
    but allows for other than .py files as well through importlib.machinery.SourceFileLoader.
    """
    import importlib.util
    import importlib.machinery

    # from_loader does not enforce .py but  importlib.util.spec_from_file_location() does.
    spec = importlib.util.spec_from_loader(
        modAsName,
        importlib.machinery.SourceFileLoader(modAsName, importedFilePath),
    )
    if spec is None:
        raise ImportError(f"Could not load spec for module '{modAsName}' at: {importedFilePath}")
    module = importlib.util.module_from_spec(spec)

    try:
        spec.loader.exec_module(module)
    except FileNotFoundError as e:
        raise ImportError(f"{e.strerror}: {importedFilePath}") from e

    sys.modules[modAsName] = module
    return module

And then I would use it as so:

aasMarmeeManage = importFileAs('aasMarmeeManage', '/bisos/bpip/bin/aasMarmeeManage.cs')
def g_extraParams(): aasMarmeeManage.g_extraParams()