我试图运行 python 脚本，但得到 ImportError:尝试相对导入，没有已知的父 package

Question

I found other stackoverflow questions and answers for this error, but none of them worked for me. My python package problem:

I tried to install packages with these commands so I could run tests:

$ pip3 install virtualenv
$ virtualenv -p $(which python3.9) venv
$ source venv/bin/activate
$ pip install --upgrade pip  # stop local environments from messing things up
$ pip install -r path/to/requirements.txt

I tried to run my tests:

$ python -m unittest discover

I got this error:

======================================================================
ERROR: some_file (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: some_file
Traceback (most recent call last):
  File "/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/unittest/loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/Users/path/some_file.py", line 3, in <module>
    from .other_file import some_function, SomeClass
ImportError: attempted relative import with no known parent package


----------------------------------------------------------------------

As the error said, I was trying to use a relative path in my file:

from .other_file import some_function, SomeClass

I don't know about other versions of python, but I expected this to be possible in python3.

Answer 1

I needed to add this line to my installation commands:

$ pip install --editable .

That is:

$ pip3 install virtualenv
$ virtualenv -p $(which python3.9) venv
$ source venv/bin/activate
$ pip install --upgrade pip  # stop local environments from messing things up
$ pip install -r path/to/requirements.txt
$ pip install --editable .

I don't yet understand why it works. I'll update this answer if I find out more.