Python3 ImportError：尝试在没有已知父项的情况下进行相对导入 package

Question

I have the following 3 python files:

• main.py

from .Constants import *

• __init__.py

• Constants.py :

CONSTANT_TEST = test

Now when I run python3 main.py i get the following error

ImportError: attempted relative import with no known parent package

Not sure what I am missing here.

Answer 1

The general rule of thumb is that you should never execute files from within the same package. My suggestion would be to create a test file and import your package into that file, then do all of your testing from within that file. For example, if your package directory looks like this:

package_tests.py

package/
    __init__.py
    main.py
    Constants.py

In package/__init__.py :

from package.Constants import CONSTANT_TEST

# import everything here that you want users to be able to access by topmost import ("import package")

In package/Constants.py :

CONSTANT_TEST = "constant"

In package/main.py :

from package.Constants import CONSTANT_TEST

# other code that utilizes CONSTANT_TEST

In package_tests.py :

import package

print(package.CONSTANT_TEST)