为什么相对导入在Python 3中不起作用？

Question

I recently upgraded from python2.7 to python3 and think it may have screwed up some configurations. Now when I try to run a module, I get import errors. Let's say I have a directory structure like this:

/directory
/directory/__init__.py
/directory/run.py
/directory/app/db.py
/directory/app/views.py
/directory/app/__init__.py

with the following imports...

/directory/run.py says 'import app'
/directory/app/db.py says 'import views'

When I execute run.py, I get an error saying the module views cannot be found. However, if I go into /directory/app and execute db.py, then the import runs correctly. I've also found that if I change the /directory/app/db.py to say "from app import views" then it works correctly when executing run.py. However, this used to all work!

It seems like the import statements are not taking into account the folder it's being executed in. It seems like this wants me to base all of my imports out of the root folder, which seems incorrect and would take me time to change everything.

Any ideas as to what happened? This has been driving me crazy.

Answer 1

In Python3, implicit relative imports have been removed, all imports need to be either absolute, or use explicit relative imports.

This is not going to change, you need to either replace them with from app import views or from . import views from . import views .

Answer 2

Python 2.x and Python 3.x differ in so many ways it is usually extremely helpful to use 2to3 or another similar tool to "port" (convert) the code.

The issue you are running into likely has to do with the fact that Python 2 uses relative imports but Python 3 uses absolute imports (I may have that backwards). It is possible to change the import statement to make the import work, though for the torrent of compatibility issues that will surely follow, I highly recommend using 2to3 and then making any final adjustments manually.

Good luck!