I have an application with embedded python. When trying to import numpy, or any other module that was installed by pip, it fails with error 'ModuleNotFoundError("No module named ...")'. Yet, on the command line python, all works fine. The problem is not in the PATH, as only specific files (those with .<pyver-platform>.pyd extensions, e.g. .cp37-win_amd64.pyd) cannot be found. 

Example1: numpy

import numpy
>> ImportError("No module named 'numpy.core._multiarray_umath')

The line which fails is:
    from . import multiarray
The file it is trying to load:
C:\Program Files\Python37\Lib\site-packages\numpy\core_multiarray_umath.cp37-win_amd64.pyd


Example 2: cv2

import cv2
>> ModuleNotFoundError("No module named 'cv2.cv2'")
The line which fails is:
from .cv2 import *
The file it is trying to load:
C:\Program Files\Python37\Lib\site-packages\cv2\cv2.cp37-win_amd64.pyd

Are you sure you don't have the 32-bit version of Python and the 64-bit version of those packages?

Yes, and note that the command line python works fine.

Where are you running the embedded Python from, and how have you configured it to include the packages?

Is your install in Program Files from the full installer? Or have you extracted the embeddable distro there?

Hi,

I have a full install of Python from the installer in:
C:\Program Files\Python37
Then, I added libraries using pip.
Everything works fine from the command line Python.

Then, I build my C++ application with VisualStudio and link to the Python DLLs. I start Python inside my app using the usual code:

  Py_SetPath(...);
  Py_SetProgramName(...);
  Py_InitializeEx(0);

  PyRun_SimpleString("import sys");
  PyRun_SimpleString("print(sys.path)");
  PyRun_SimpleString("print(sys.prefix)");
  PyRun_SimpleString("print(sys.executable)");


>> ['C:\\Program Files\\Python37\\DLLs', 'C:\\Program Files\\Python37\\Lib', 'C:\\Program Files\\Python37', 'C:\\Program Files\\Python37\\Lib\\site-packages']
>> C:\Program Files\Python37
>> C:\Program Files\Python37\python.exe

So, everything works fine at this point. If I run the following:

  PyRun_SimpleString("import numpy");


>> ImportError("No module named 'numpy.core._multiarray_umath'")

Problem solved:

Running the following code in the CommandLine Python and in the C++ embedded python clarified the problem:

  import importlib.machinery
  print(importlib.machinery.all_suffixes())
  
CommandLine Python:
> ['.py', '.pyw', '.pyc', '.cp37-win_amd64.pyd', '.pyd']

C++ Embedded Python:
> ['.py', '.pyw', '.pyc', '_d.cp37-win_amd64.pyd', '_d.pyd']

It shows that the Embedded python is running in Debug mode and therefore adds a _d to the suffix. Yet the numpy or pytorch installed only non-debug files.

I'm closing the issue, see my previous post.