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Say I have a Python project that looks like this:

project/ ├── package/ │ ├── __init__.py │ ├── module1.py └── main.py

I would like package/ to be self-contained, though it is called from main.py.

Here are the contents of package/module1.py:

def some_fn(): print("hi")

now say I want to call some_fn inside __init__.py. I have the following options:

1:

import module1
  • Benefit: can call when executing in package/
  • Drawback: fails to import when executing outside of package/

2:

import package.module1
  • Benefit: imports outside of package/
  • Drawback: fails to import when inside of package/

3:

import os import sys sys.path.append(os.path.dirname(os.path.abspath(__file__))) import module1
  • Benefit: covers both cases
  • Drawback: ugly

Is there a preferred or idiomatic way of doing this?

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  • 1
    Not a direct answer to your question, but are you aware that you can make the package executable by adding a __main__ module?
    – JimmyJames supports Canada
    CommentedDec 9, 2024 at 19:00
  • 4
    Do not go down the route of sys.path manipulation. That gets really difficult to debug. Instead, define a shared/global module namespace hierarchy. You can define multiple command line entrypoints, and can re-export objects under different names. You can also use relative imports like from . import module1 so that a module doesn't have to know its place in the module hierarchy, which makes it easier to move a package around. The drawback of scripts/entrypoints is that your project must be installed, ideally in a venv. Modern tools like poetry or uv make this a lot easier than pip.
    – amon
    CommentedDec 9, 2024 at 19:42
  • @JimmyJames I am familiar with __main__.py and how it will enable you to python -m my_module, but does it help with relative imports?
    – Leftover Salad
    CommentedDec 10, 2024 at 16:42
  • @amon thanks for the response, an issue with relative imports like from . import module1 is I cannot use it independently, I would get the error: ImportError: attempted relative import with no known parent package
    – Leftover Salad
    CommentedDec 10, 2024 at 16:56
  • I'm not sure why you can't use relative imports inside the package and absolute imports from outside the package. Are you trying to build a module that's both called from within a package and from a non-package context?
    – JimmyJames supports Canada
    CommentedDec 10, 2024 at 16:59

1 Answer 1

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That relative imports work differently depending on whether you are in a package context or not is one the 'features' of Python that annoys me and I have never really understood the need or reason for it (anyone who knows please comment.) It seems like a workaround for some sort of 'painting oneself into a corner' type of mistake.

In any event that's how it works in Python. Here's a question on SO with a bunch of different answers and approaches so I don't see a need to reiterate what is already there.

My personal approach is to accept that once I have decided to go the package route, I commit to that and use the package-style imports for all use cases. One situation where that becomes a challenge is if you have multiple modules that can be run as standalone scripts e.g., with a __name__ == "__main__": check and you want to make a package from those modules. In that scenario, I've taken to changing the if statement to a method definition and then using the excellent typer library to create a CLI that calls those methods. The effort required to create a CLI with typer is so low that I don't even bother with other approaches.

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