How to resolve this import error in Python 3.6?

Question

I have a very simple namespace package: https://github.com/korommatyi/import-error-repro (I describe the directory layout below). If I try to import namespace_repro.module, I got the following error: AttributeError: module 'namespace_repro' has no attribute 'module'. As far as I understand my package has a valid layout and the import should work. Interestingly, the error is present only in Python 3.6.8 and the import succeeds in Python 3.7.

How to reproduce the problem?

I created a brand new Python 3.6 conda environment by conda create -n namespace6 python=3.6 ipython, then I activated it and installed the package as pip install -e ./import-error-repro (note that -e doesn't matter, the problem is reproducible without it). After that, I tried import namespace_repro.module in ipython (though the same happens in the official python interpreter). The result is

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-1-bcae5a697dad> in <module>
----> 1 import namespace_repro.module

~/namespace-repro/src/namespace_repro/module/__init__.py in <module>
----> 1 from namespace_repro.module.x import x

~/namespace-repro/src/namespace_repro/module/x.py in <module>
----> 1 import namespace_repro.module.y as y
      2 
      3 x = y.y

AttributeError: module 'namespace_repro' has no attribute 'module'
---------------------------------------------------------------------------

The strange thing is that the import system finds namespace_repro.module twice but fails at the third time!

Some other interesting behaviour:

In [1]: import namespace_repro.module.y as y  # This doesn't work.
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-4035347ea59b> in <module>
----> 1 import namespace_repro.module.y as y

AttributeError: module 'namespace_repro' has no attribute 'module'

In [2]: import namespace_repro.module.y  # But this one does! Why?

In [3]: dir(namespace_repro.module.y) # The error returns when we actually want to use the module.
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-3-d89bcfd9e509> in <module>
----> 1 dir(namespace_repro.module.y)

AttributeError: module 'namespace_repro' has no attribute 'module'

In [4]: from namespace_repro.module.y import y  # This works fine!

In [5]: y
Out[5]: True

Directory layout

. import-error-repro
+-- setup.py
+-- src
|   +-- namespace_repro
|   |   +-- module
|   |   |   +-- __init__.py
|   |   |   +-- x.py
|   |   |   +-- y.py

Answer 1

这是CPython错误30024，毫不奇怪，该错误已在3.7中修复。请注意，从3.5开始，具有相对（圆形）导入的更惯用的形式开始起作用。