Sample Code for calling Python functions in C

When using the C language, we sometimes encounter the need to call Python functions to complete some specific functions. Next, we will introduce in detail how C calls Python functions and hope to help you.

Python script, saved as pytest. py

 
 

  
  
def add(a,b):  
  
  
print "in python function add"  
  
  
print "a = " + str(a)  
  
  
print "b = " + str(b)  
  
  
print "ret = " + str(a+b)  
  
  
return a + b 
 
 

Example code for C to call a Python function:

 
 

  
  
# Include <stdio. h>
  
  
# Include <stdlib. h>
  
  
# Include "C:/Python26/include/python. h"
  
  
# Pragma comment (lib, "C :\\ Python26 \ libs \ python26.lib ")
  
  
Int main (int argc, char ** argv)
  
  
{
  
  
// Initialize Python
  
  
// Before using the Python system, you must use Py_Initialize
  
  
// Perform initialization. It loads Python built-in modules and adds the system path.
  
  
// Path to the module search path. This function has no return value. Check the system
  
  
// Use Py_IsInitialized to check whether the initialization is successful.
  
  
PyObject * pName, * pModule, * pDict, * pFunc, * pArgs, * pRetVal;
  
  
Py_Initialize ();
  
  
// Check whether Initialization is successful
  
  
If (! Py_IsInitialized ())
  
  
{
  
  
Return-1;
  
  
}
  
  
// Load the script named pytest (Note: It is not pytest. py)
  
  
PName = PyString_FromString ("pytest ");
  
  
PModule = PyImport_Import (pName );
  
  
If (! PModule)
  
  
{
  
  
Printf ("can't find pytest. py ");
  
  
Getchar ();
  
  
Return-1;
  
  
}
  
  
PDict = PyModule_GetDict (pModule );
  
  
If (! PDict)
  
  
{
  
  
Return-1;
  
  
}
  
  
// Find the function named add
  
  
PFunc = PyDict_GetItemString (pDict, "add ");
  
  
If (! PFunc |! PyCallable_Check (pFunc ))
  
  
{
  
  
Printf ("can't find function [add]");
  
  
Getchar ();
  
  
Return-1;
  
  
}
  
  
// Stack parameters
  
  
PArgs = PyTuple_New (2 );
  
  
// PyObject * Py_BuildValue (char * format ,...)
  
  
// Convert the C ++ variable into a Python object. When you need
  
  
// This function is used when C ++ passes a variable to Python. This function
  
  
// A bit similar to C's printf, but the format is different. Common formats include:
  
  
// S indicates a string,
  
  
// I indicates an integer variable,
  
  
// F indicates a floating point number,
  
  
// O indicates a Python object.
  
  
PyTuple_SetItem (pArgs, 0, Py_BuildValue ("l", 3 ));
  
  
PyTuple_SetItem (pArgs, 1, Py_BuildValue ("l", 4 ));
  
  
// Call the Python Function
  
  
PRetVal = PyObject_CallObject (pFunc, pArgs );
  
  
Printf ("function return value: % ld \ r \ n", PyInt_AsLong (pRetVal ));
  
  
Py_DECREF (pName );
  
  
Py_DECREF (pArgs );
  
  
Py_DECREF (pModule );
  
  
Py_DECREF (pRetVal );
  
  
// Close Python
  
  
Py_Finalize ();
  
  
Return 0;
  
  
}
  
  
// Another method for personal practice
  
  
# Include <Python. h>
  
  
# Include <conio. h>
  
  
Int main ()
  
  
{
  
  
Py_Initialize ();
  
  
If (! Py_IsInitialized ())
  
  
{
  
  
Printf ("initialization error \ n ");
  
  
Return-1;
  
  
}
  
  
PyObject * pModule = NULL;
  
  
PyObject * pFunc = NULL;
  
  
PyObject * pArg = NULL;
  
  
PyObject * pRetVal = NULL;
  
  
PModule = PyImport_ImportModule ("hello ");
  
  
PFunc = PyObject_GetAttrString (pModule, "hello ");
  
  
PArg = Py_BuildValue ("(I, I)", 33,44 );
  
  
PRetVal = PyObject_CallObject (pFunc, pArg );
  
  
Printf ("% d \ n", PyInt_AsLong (pRetVal ));
  
  
Py_Finalize ();
  
  
_ Getch ();
  
  
Return 0;
  
  
}
 
 

The above is an introduction to the operation methods related to calling Python functions in C.