模块中的Python绝对导入失败

Question

I have a project which looks like this:

my_project/
          __init__.py -- empty
          run.py
          datacheck/
                  __init__.py -- empty
                  datacheck.py -- containing class DataCheck(object)
                  config.py -- containing BusinessConfig(object)
                  business.py -- containing class BusinessCheck(DataCheck)

My PYTHONPATH is configured to have /my_project in it.

In run.py, I have the following code:

from datacheck.business import BusinessCheck
business = BusinessCheck()
business.check_data()

In business.py, I have the following imports that fail:

from datacheck.config import BusinessConfig
from datacheck.datacheck import DataCheck

A relative import like from .config import BusinessConfig works - however I've read in numerous threads that an absolute import is preferred.

To do a simple test, I also created the following:

myproject/
          __init__.py -- empty
          run_test.py
          test/
              __init__.py -- empty
              test1.py -- containing class Test1(object)
              test2.py -- containing class Test2(Test1)

run_test.py imports and runs the Test2 class, this didn't fail.

It left me a bit flabbergasted, I don't understand why my absolute imports in datacheck are not working - can anyone explain?

Answer 1

You should prefer absolute imports if your module can be used as __main__ , as explained in the documentation . If not, relative imports are fine.

These imports fail, because your package datacheck contains a module datacheck (same name). When looking up the name, Python implicitly looks inside the package first. There, it finds the module datacheck . This module, however, does not contain anything with the name config , so the import fails.

If you want to use absolute imports, move all the stuff from the module datacheck into the __init__.py of the package, or rename it.

Answer 2

I know this is many years later, but for the sake of others searching here, I was able to resolve a similar problem with this bit of code:

from __future__ import absolute_import

After that, absolute imports worked fine in Python 2.6 and 2.7.