Python Embedding in C++ : ImportError: No module named pyfunction

Question

Hi I\'m trying to embed python (2.7) into C++ (g++ 4.8.2) and hence call a python function from C++. This is the basic code provided in python documentation for embedding:

Answer 1

For anyone else having this problem:

Are you sure that your .py file lies in the same directory where C++ executable is?

I was programming in CLion and forgot that executable lies in cmake-build-debug. So I added .py file in project directory and no no surprise I was getting the same error ImportError. I placed .py file to cmake-build-debug (executable file by default lies there), used answers from this question and everything worked!

Answer 2

You can also try to include these code to your c program

Py_Initialize();
PyObject *sys = PyImport_ImportModule("sys");
PyObject *path = PyObject_GetAttrString(sys, "path");
PyList_Append(path, PyUnicode_FromString("."));

Learn from Here

Answer 3

Hi to all those facing the same problem, I found the solution! setenv() is a function defined in stdlib.h which sets the environment variable. Just have to run it!

setenv("PYTHONPATH",".",1);

for more info on setenv:

$ man setenv

All the best :) Also, thanks to @spinus

Answer 4

Put the following in the C/C++ code, just after Py_Initialize();

PyRun_SimpleString("import sys");
PyRun_SimpleString("sys.path.append(\".\")");

Answer 5

the solution provided by spinus works if the python file does not import any additional python-library.

However, if a python file imports an additional library, lets say numpy, the above code crashes as follows:

:~/programs/python$ ./a.out myModule multiply 4 3
Traceback (most recent call last):
  File "/home/a/programs/python/myModule.py", line 1, in <module>
    import numpy
ImportError: No module named 'numpy'
Failed to load "myModule"

As a remark, the import of the python-library from C does not work:

PyObject *pNumpy = PyUnicode_FromString("numpy");
PyObject *pModuleA = PyImport_Import(pNumpy); 

Does someone know how to call from C python-functions, which depend of some other python-libraries?

Answer 6

Try this one:

 $ PYTHONPATH=. ./call_function pyfunction multiply 2 3

if this won't work, try to make __init__.py file in this directory and try again.

UPDATE:

I think that PYTHONPATH is temporary solution, to test stuff. If you want to have a directory when all your embedded modules lives you have to put in your embedded interpreter something equilevant to this:

import sys
sys.path.insert(0, "./path/to/your/modules/")

You can do it probably in python in your interpreter or on C level. This will add search path in very similar manner as PYTHONPATH but it is more persistant and elegant (IMHO).