为什么无法加载模块？

Question

Display my project 's directory structure:

tree project
project
├── config.py
├── __init__.py
└── project.py

Content in project.py:

from . import config

def main():
    pass

if __name__ == '__main__':
    main()

Content in __init__.py :

__all__ = ['project','config']
from project import * 
from . import config

config.py is blank for simplicity.

To load the module:

cd  project
import project

It encounter the error info: Parent module '' not loaded, cannot perform relative import

Why can't import project ? I found that if project.py renamed as myproject.py , keep any other thing the same as before, import project can work.
Does not the package project share same name with module project.py ?
Why same names matter?

Answer 1

If you try to look at __package__ from project.py , you will see that it changes from nothing when you import project inside the project/ folder, and when you import project just outside the folder. This is because, when you are inside the folder, you are importing the module project (ie the project.py file), and from outside the project/ folder you are importing the project package (ie the you are running the __init__.py file).

When writing from. import x from. import x , you expect to import x from inside the current package, but there is no package context, therefore it cannot import.

Answer 2

According to this answer: https://stackoverflow.com/a/35710527/4393278

What does __all__ do?

It declares the semantically "public" names from a module. If there is a name in all , users are expected to use it, and they can have the expectation that it will not change.

` all = ['foo', 'Bar'] means that when you import * from the module, only those names in the all are imported.

So you don't need to define __all__ if you want to import anything inside project.py file. Also I think you should import a file is not by their path. So, inside your __init__ file, it should be like this.

from .project import *
from .config import *