Import arbitrary python source file. (Python 3.3+)

Question

How can I import an arbitrary python source file (whose filename could contain any characters, and does not always ends with .py) in Python 3.3+?

I used imp.load_module as follows:

>>> import imp >>> path = '/tmp/a-b.txt' >>> with open(path, 'U') as f: ...     mod = imp.load_module('a_b', f, path, ('.py', 'U', imp.PY_SOURCE)) ... >>> mod <module 'a_b' from '/tmp/a-b.txt'> 

It still works in Python 3.3, but according to imp.load_module documentation, it is deprecated:

Deprecated since version 3.3: Unneeded as loaders should be used to load modules and find_module() is deprecated.

and imp module documentation recommends to use importlib:

Note New programs should use importlib rather than this module.

What is the proper way to load an arbitrary python source file in Python 3.3+ without using the deprecated imp.load_module function?

Answer 1

Found a solution from importlib test code.

Using importlib.machinery.SourceFileLoader:

>>> import importlib.machinery >>> loader = importlib.machinery.SourceFileLoader('a_b', '/tmp/a-b.txt') >>> mod = loader.load_module() >>> mod <module 'a_b' from '/tmp/a-b.txt'> 

NOTE: only works in Python 3.3+.

UPDATE Loader.load_module is deprecated since Python 3.4. Use Loader.exec_module instead:

>>> import types >>> import importlib.machinery >>> loader = importlib.machinery.SourceFileLoader('a_b', '/tmp/a-b.txt') >>> mod = types.ModuleType(loader.name) >>> loader.exec_module(mod) >>> mod <module 'a_b'> 

---

>>> import importlib.machinery >>> import importlib.util >>> loader = importlib.machinery.SourceFileLoader('a_b', '/tmp/a-b.txt') >>> spec = importlib.util.spec_from_loader(loader.name, loader) >>> mod = importlib.util.module_from_spec(spec) >>> loader.exec_module(mod) >>> mod <module 'a_b' from '/tmp/a-b.txt'> 

Answer 2

Updated for Python >= 3.8:

Short version:

>>> # https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly >>> import importlib.util, sys >>> spec = importlib.util.spec_from_file_location(modname, fname) >>> module = importlib.util.module_from_spec(spec) >>> sys.modules[modname] = module >>> spec.loader.exec_module(module) 

Full version:

>>> import importlib.util >>> import sys >>> from pathlib import Path >>> from typing import TYPE_CHECKING >>>  >>>  >>> if TYPE_CHECKING: ...     import types ... ... >>> def import_source_file(fname: str | Path, modname: str) -> "types.ModuleType": ...     """ ...     Import a Python source file and return the loaded module.  ...     Args: ...         fname: The full path to the source file.  It may container characters like `.` ...             or `-`. ...         modname: The name for the loaded module.  It may contain `.` and even characters ...             that would normally not be allowed (e.g., `-`). ...     Return: ...         The imported module  ...     Raises: ...         ImportError: If the file cannot be imported (e.g, if it's not a `.py` file or if ...             it does not exist). ...         Exception: Any exception that is raised while executing the module (e.g., ...             :exc:`SyntaxError).  These are errors made by the author of the module! ...     """ ...     # https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly ...     spec = importlib.util.spec_from_file_location(modname, fname) ...     if spec is None: ...         raise ImportError(f"Could not load spec for module '{modname}' at: {fname}") ...     module = importlib.util.module_from_spec(spec) ...     sys.modules[modname] = module ...     try: ...         spec.loader.exec_module(module) ...     except FileNotFoundError as e: ...         raise ImportError(f"{e.strerror}: {fname}") from e ...     return module ... >>> import_source_file(Path("/tmp/my_mod.py"), "my_mod") <module 'my_mod' from '/tmp/my_mod.py'> 

Original answer for Python 3.5 and 3.6

Shorter version of @falsetru 's solution:

>>> import importlib.util >>> spec = importlib.util.spec_from_file_location('a_b', '/tmp/a-b.py') >>> mod = importlib.util.module_from_spec(spec) >>> spec.loader.exec_module(mod) >>> mod <module 'a_b' from '/tmp/a-b.txt'> 

I tested it with Python 3.5 and 3.6.

According to the comments, it does not work with arbitrary file extensions.