How to embed Python matplotlib in C++?

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C++

Python

DLL

VBA

Hello,

i'm trying to develop a dll that embeds python. I am using boost 1.72 and python 3.7

The dll exports some function to initialize python, adds some numpy array and launches a script. I created a VBA macro in excel that calls the dll function.

the function are:

long __stdcall Init(); //initialize python
long __stdcall AddInput(double* data, long nRows, long nCols, const char* label); //adds input
long __stdcall ExecFile(const char* file); //execs a python script
void __stdcall Clear();

everything works fine as long as I don't import matplotlib.
Infact if I try to import matplotlib.pyplot in python script and plot an array an exception is thrown.
How can I use matplotlib.pyplot in script called from a dll embedding python?


the script i'm trying to exec is

import numpy as np
import matplotlib.pyplot as plt
import sys


def main():
	try:
		sys.stdout = open("outPy.log","w")
		
		plt.plot([1,2,4],[1,2,3])
		plt.show()
	except:
		print("Unexpected error:", sys.exc_info()[0])
		print("Unexpected error:", sys.exc_info()[1])
		print("Unexpected error:", sys.exc_info()[2])
	finally:
		sys.stdout.close()
	
	

if __name__ == '__main__':
   main()

the exception is:

Unexpected error: <class 'IndexError'>
Unexpected error: list index out of range
Unexpected error: <traceback object at 0x2061C030>

What I have tried:

Is this because I'am calling the dll from VBA?

Is it a question of thread?