Circular imports for Python 3.8 on Windows if DLLs are already loaded

WIth fiona 1.8.15, the issue is fixed now in the conda-forge builds, only the Windows py3.8 build is still failing: https://github.com/conda-forge/fiona-feedstock/pull/167

The failure is with the general error message of partially initialized module, so doesn’t give much pointers (at least to me):

running run_test.py
Traceback (most recent call last):
  File "D:\bld\fiona_1599200296823\test_tmp\run_test.py", line 6, in <module>
    import fiona
  File "D:\bld\fiona_1599200296823\_test_env\lib\site-packages\fiona\__init__.py", line 84, in <module>
    import fiona._loading
  File "D:\bld\fiona_1599200296823\_test_env\lib\site-packages\fiona\_loading.py", line 44, in <module>
    import fiona.ogrext
  File "fiona/ogrext.pyx", line 29, in init fiona.ogrext
  File "D:\bld\fiona_1599200296823\_test_env\lib\site-packages\fiona\env.py", line 14, in <module>
    with fiona._loading.add_gdal_dll_directories():
AttributeError: partially initialized module 'fiona' has no attribute '_loading' (most likely due to a circular import)

_Originally posted by @jorisvandenbossche in https://github.com/Toblerity/Fiona/issues/941#issuecomment-686982973_

[fargiolas]

Probably a different bug, but I’m seeing a similar circular import error when I import geopandas (fiona 1.18.18, geopandas 0.9.0, gdal 3.2.2, installed with pip and brew on macos). The error goes away if I import fiona before geopandas.

[ogelin]

Hi, on MacOS using pip installs I also had this error when importing geopandas. Python 3.9.2.

I changed pyproj from 3.0.1 to 3.0.0 and now the error goes away as long as I import fiona before geopandas.

If I only import geopandas without fiona first, I still get the “Circular import” error message that others reported.