Python cannot import name

问题:

I've been wrestling most of the night trying to solve an import error.

This is a common issue, but no previous question quite answers my issue.

I am using PyDev (an Eclipse plugin), and the library Kivy (a Python library)

I have a file structure set up like this:

<code>
    __init__.py
    main.py
    engine.py
    main_menu_widget.py

"code" is held within the eclipse folder "MyProject" but it's not a package so I didn't include it.

The files look like this:

main.py

# main.py
from code.engine import Engine

class MotionApp(App):
    # Ommited

engine.py

# engine.py
from code.main_menu_widget import MainMenuWidget

class Engine():
    # Ommited

main_menu_widget.py

# main_menu_widget.py
from code.engine import Engine

class MainMenuWidget(Screen):
    pass

The error I recieve, in full detail, is:

 Traceback (most recent call last):
   File "C:\MyProject\code\main.py", line 8, in <module>
     from code.engine import Engine
   File "C:\MyProject\code\engine.py", line 6, in <module>
     from code.main_menu_widget import MainMenuWidget
   File "C:\MyProject\code\main_menu_widget.py", line 3, in <module>
     from code.engine import Engine

Any idea what I did wrong here? I just renamed my entire folder structure because I screwed up this module structure so bad, but I think i'm close to how it should look....

回答1:

There seems to be a circular import. from engine.py you are importing main_menu_widget while from main_menu_widgetyou are importing engine.

That is clearly a circular import which is not allowed by python.

回答2:

it's in the same folder, use a relative package name (it's a good practice to do so anyway):

from .engine import Engine

回答3:

Your code directory is a package. Ensure that the directory above it, i.e C:\MyProject judging from your error messages, is in your PYTHONPATH.

Open the context menu by selecting your project and clicking your mouse's right button, then select Properties. Select PyDev - PYTHONPATH and from there the Source folders tab. Check that the directory mentioned above is present; if it isn't press Add source folder, select it from the dialogue and press OK.