$ tail -n999 a/*.py
==> a/b.py <==
from a.c import d

e = 1

==> a/c.py <==
from a.b import e

d = 1

==> a/__init__.py <==

$ python3.8 -c 'import a.b'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/tmp/x/a/b.py", line 1, in <module>
    from a.c import d
  File "/tmp/x/a/c.py", line 1, in <module>
    from a.b import e
ImportError: cannot import name 'e' from 'a.b' (/tmp/x/a/b.py)

$ ~/workspace/cpython/python -c 'import a.b'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/tmp/x/a/b.py", line 1, in <module>
    from a.c import d
  File "/tmp/x/a/c.py", line 1, in <module>
    from a.b import e
ImportError: cannot import name 'e' from 'a.b' (partially initialized module -- most likely due to a circular import) (/tmp/x/a/b.py)