pylibkriging import fails on Windows

[hpwxf]

on: Python 3.9.5

$ pip install pylibkriging
Collecting pylibkriging
  Downloading pylibkriging-0.4.1-cp39-cp39-win_amd64.whl (252 kB)
     |████████████████████████████████| 252 kB ...
Installing collected packages: pylibkriging
Successfully installed pylibkriging-0.4.1

But

ImportError: DLL load failed while importing pylibkriging: The specified module could not be found.

[yannrichet]

Is numpy version OK ? >=1.20

[hpwxf]

Python 3.7 + Windows : OK
But
Python 3.8 or 3.9 + Windows : fails (same DLL load error).

• openblas.dll is not embedded in python DLL

[hpwxf]

NB: when it fails because sub-DLL is missing, the error is ImportError: DLL load failed: The specified module could not be found.

Moreover, using Dependencies, we can see minor differences between .pyd (dll) file from releases 3.6 (<), 3.7 (#) and 3.8 (>).

• apisets : Same
• apisetsdll : Same
• chain :

< □ pylibkriging.cp36-win_amd64.pyd (ROOT) : G:/python-artifact/pylibkriging-0.4.1-cp36-cp36m-win_amd64/pylibkriging.cp36-win_amd64.pyd
< |  □ python36.dll (Environment) : C:\Python36\python36.dll
---
# □ pylibkriging.cp37-win_amd64.pyd (ROOT) : G:/python-artifact/pylibkriging-0.4.1-cp37-cp37m-win_amd64/pylibkriging.cp37-win_amd64.pyd
# |  □ python37.dll (Environment) : C:\Python37\python37.dll
---
> □ pylibkriging.cp38-win_amd64.pyd (ROOT) : G:/python-artifact/pylibkriging-0.4.1-cp38-cp38-win_amd64/pylibkriging.cp38-win_amd64.pyd
> |  □ python38.dll (Environment) : C:\Python38\python38.dll

• exports :

< Export 1 :
<         Name : PyInit_pylibkriging
<         VA : 0xE550
---
# Export 1 :
#         Name : PyInit_pylibkriging
#         VA : 0xE570
---
> Export 1 :
>         Name : PyInit_pylibkriging
>         VA : 0xE210

• imports :

< Import from module python36.dll:
# Import from module python37.dll:
many Function PyThread_* between 3.6 and 3.7 (not 3.7 and 3.8 except the following)
> Import from module python38.dll :
>        Function _Py_Dealloc

• knowndll : Same
• manifest : Same (except DLL name)
• modules :

< [ROOT] pylibkriging.cp36-win_amd64.pyd : G:/python-artifact/pylibkriging-0.4.1-cp36-cp36m-win_amd64/pylibkriging.cp36-win_amd64.pyd
# [ROOT] pylibkriging.cp37-win_amd64.pyd : G:/python-artifact/pylibkriging-0.4.1-cp37-cp37m-win_amd64/pylibkriging.cp37-win_amd64.pyd
> [ROOT] pylibkriging.cp38-win_amd64.pyd : G:/python-artifact/pylibkriging-0.4.1-cp38-cp38-win_amd64/pylibkriging.cp38-win_amd64.pyd
< [Environment] python36.dll : C:\Python36\python36.dll
# [Environment] python37.dll : C:\Python37\python37.dll
> [Environment] python38.dll : C:\Python38\python38.dll

• sxsentries :

< [-] sxs dependencies for executable : G:/python-artifact/pylibkriging-0.4.1-cp36-cp36m-win_amd64/pylibkriging.cp36-win_amd64.pyd
---
# [-] sxs dependencies for executable : G:/python-artifact/pylibkriging-0.4.1-cp37-cp37m-win_amd64/pylibkriging.cp37-win_amd64.pyd
---
> [-] sxs dependencies for executable : G:/python-artifact/pylibkriging-0.4.1-cp38-cp38-win_amd64/pylibkriging.cp38-win_amd64.pyd

[hpwxf]

See also #86.

[hpwxf]

Is numpy version OK ? >=1.20

Yes, for all configurations:

 pip show numpy
Name: numpy
Version: 1.20.3

[hpwxf]

Seems to be a common issue between Python 3.7 and 3.8

• https://bugs.python.org/issue42339
• Python 3.8: ImportError: DLL load failed while importing _psycopg: The specified module could not be found. psycopg/psycopg2#1006

[hpwxf]

(cf https://stackoverflow.com/a/62891703/12430075)

It could be that your C++ python library itself depends on a shared library / DLL. Python 3.7/3.6 would search for DLLs in PATH or the current working directory, but this is no longer the case in Python 3.8:

https://docs.python.org/3.8/whatsnew/3.8.html#ctypes

If this is the problem, you can add use add_dll_directory() to tell Python 3.8 where it should look for the DLLs.