Allow very long "from .." imports for black in order to stick to max line length?

Question

In our projects instead of using relative imports, we usually create the code as python packages and install them with pip install -e . This is nice and prevents from issues with import errors on different machines/IDEs. However, for bigger project with a deeper structure this however means quite long import statements, which is where problem with black starts. E.G the following (dummy) example import

from root.machine_vision.hardware_layer.cameras.some_camera_brand. \
    camera_access_class import CameraAccessClass

would be changed by black into

from root.machine_vision.hardware_layer.cameras.some_camera_brand.camera_access_class import (
    CameraAccessClass
)

Which would cause issues with the max. line length. So far I have only found this post, which suggests to turn black off for the block in question with # fmt: off and # fmt: on. I'm wondering if it is possible to tell black to allow backslashes in these kind of imports.

On the other hand, is there maybe another way to handle such long imports? For example some way to do "part imports", which would look something like

import root.machine_vision.hardware_layer as hwl
from hwl.cameras.some_camera_brand.camera_access_class import CameraAccessClass

So far I have not found a satisfactory solution...

score 2 · Accepted Answer · answered Jul 11 '23 at 13:44

Despite the surface similarities, there is a distinct difference between a fully qualified module name like root.machine_vesion.hardware_layer.cameras and an expression like hwl.cameras. hwl is a variable that refers to a particular package, not the name of that package, and whether that package has an attribute named cameras is determined by the package itself.

Assuming the package root.machine_version.hardware_layers does exposes cameras as an attribute, (and each lower package exposes the necessary module as an attribute as well) you could write

import root.machine_vision.hardware_layer as hwl
CameraAccessClass = hwl.cameras.some_camera_brand.camera_access_class.CameraAccessClass

The following

from hwl.cameras.some_camera_brand.camera_access_class import CameraAccessClass

would not work because the import statement requires a module name, not an expression that evaluates to a module object.

Allow very long "from .." imports for black in order to stick to max line length?

1 Answers1