Import all (*) from modules better be positioned before explicit local imports

[besfahbod]

In general, it's recommended to not use "import all" pattern, or at least not without explicit __all__ defined.

However, many code-bases still do so, for good reasons, such as reducing friction in adding new items to a shared library.

Now, assuming we're okay with import * in general, and specifically from _<dir-name> import * forms, the example below demonstrates a problem when having import * statement at the end of the local-imports list, instead of first.

---

Here's the structure of the package bar, which has an internal module _foo, as well as module _bar that's considered the "main" module of the package.

The file contents are like:

bar/__init__.py:

from ._foo import Any, All, Not # ...
from ._bar import *

# [...]

bar/_bar.py:

from typing import Any, List # ...

# [...]

bar/_foo.py:

class Any(...):
    # [...]

class All(...):
    # [...]

class Not(...):
    # [...]

# [...]

In this set up, the class Any from typing is overshadowing the class Any defined in bar/_foo.py, and re-export explicitly as part of the "public API" of package bar.

If we change keep import * statements at the beginning of local-imports block, we would prevent such implicit overrides from external imports, reducing friction for developers.

So, isort would modify bar/__init__.py to look like:

from ._bar import *
from ._foo import Any, All, Not # ...

# [...]

---

I don't know if this has been discussed before (really hard to search for terms "import" and "all" in this repo), but like to suggest updating isort to change the behavior here.

What do you think?

[timothycrosley]

@besfahbod I think this is a great idea! This will likely surprise many who encounter, as all other non strictly alphabetical sorting behaviour does, but I think that can be solved with some documentation updates. Overall, I think this the exact kind of refinement that I'd love to include in isort now that it is a more mature tool.

Thanks!

~Timothy

[besfahbod]

Thanks, @timothycrosley! Agreed.

Not sure if most people agree or not, but something I've been doing personally has been to even keep import * statements in a separate block from explicit-import statements. If we do that, we can keep maintaining the promise of "always alphabetical order per block". #mytwocents

[timothycrosley]

This has been implemented in develop (using the new --star-first option) with plans to make default in next major release.

Thanks!

~Timothy