Explicit relative imports

[Aymeric Augustin]

Hello,

We’ve started using explicit relative imports in newer parts of the Django source tree. They’re short and readable. That’s good.

I would like to add guidelines about imports in the coding style guide in order to improve consistency.

My inclination would be to recommend relative imports within “components” but avoid them between “components”, where a component is:

- a well-defined sub-framework (django.core.cache, django.db, django.forms, django.template, etc.)
- a contrib app
- an app in the tests/ directory
- etc.

I would discourage going back into parent modules with relative imports because statements such as `from ...spam import eggs` are hard to parse.

You can see an example of this style in django.apps which has only three files.

What do you think?

--
Aymeric.

[Marc Tamlyn]

I agree wholeheartedly. (Sorry, not much else to say...)

--
Aymeric.



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[Florian Apolloner]

Parent imports inside the sub-framework could make sense, otherwise the mixture of imports might look odd. As long as it stops at ".." and doesn't include more it's relatively fine imo.

Cheers,
Florian

[Zach Borboa]

Aymeric, is this the example?

	from .config import AppConfig # NOQA
	from .registry import apps # NOQA

from https://github.com/django/django/blob/master/django/apps/__init__.py

[Aymeric Augustin]

Hi Zach,

django/apps/registry.py is a better example. It has relative imports from django/apps/config.py and absolute imports from other parts of Django.

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Aymeric.

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Aymeric.

[Jannis Leidel]

Yup, the way to go.

Jannis

[Tom Christie]

Contrary voice here, but I don't dig explicit relative imports, it's just adds an extra decision point for no real benefit.

Personally I always recommend full absolute imports, ordered strictly alphabetically - there's then never any room for confusion or decision making around how the imports should be written, and it's always tidy and consistent.

Not looking to necessarily change the Django project's stance on that, but that's the style I use throughout my projects and it's trivial to stick to. 

Cheers,

  Tom

[Marc Tamlyn]

Whilst I think it's a bit nicer to be explicit in smaller projects, there are a few places where django's structure can result in long import paths - e.g. django.contrib.gis.db.backends where I think relative imports would actually add clarity.

I tend to separate the relative section as the last block at the end of the imports which further show what is "within" a component, rather than it being buried within a large block.

In any case, explicit relative imports are greatly preferable to implicit ones.

Marc

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[Tai Lee]

I also don't see much benefit in using relative imports. Code is read many more times than it is written, and I find having the full path makes it much easier to sort and visually scan imports, and to easily see at a glance exactly where to find what you need.

If they are to be used, I would recommend against any relative imports from parent packages. It should be limited to siblings only.

Cheers.

Tai.

[tomv]

Tom, there's another way to remove confusion/decision making about import ordering: https://pypi.python.org/pypi/isort 

For Django it could be mentioned on the contrib docs and `isort --check-only` run with flake8.

[Tim Graham]

I hope to get flake8 running on pull request builds soon. Then (unless there are objections) I will take a look at isort and see if it'll work for us in a similar fashion. From my perspective it would be great to get those checks automated so it's one less thing to think about during code reviews.