Functions required for Python to embed C/C ++ (lower-level embedding)

Embed Python into C/C ++ at a lower level, or if you want to get the values returned by a Python script, if you want to write a C program using related functions, you want to have a better understanding of how to embed Python into C/C ++ at a lower level, you can browse the following articles. Because Python has its own data type, you must use a special API to operate the corresponding data type in the C program. Common functions are as follows.

Number and string processing
The Python/c api provides the Py_BuildValue () function to convert numbers and strings to the corresponding data type in Python. The function prototype is as follows.

PyObject * Py_BuildValue (const char * format ,...)

The parameter meanings are as follows.

· Format: format the string, as shown in Table 8-1.

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The remaining parameters in the Py_BuildValue () function are integer, floating point, or string values in the C language to be converted. The returned value is a pointer of the PyObject type. In C, all Python types are declared as PyObject.

List operations

Python/c api provides the PyList_New () function to create a new Python list. The Return Value of the PyList_New () function is the list created. The function prototype is as follows.

PyObject * PyList_New (Py_ssize_t len)

The parameter meanings are as follows.

· Len: the length of the created list. After the list is created, you can use the PyList_SetItem () function to add items to the list. The function prototype is as follows.

 
 

  
  
int PyList_SetItem( PyObject *list, Py_ssize_t index,
 PyObject *item) 
 
 

The parameter meanings are as follows.

· List: list of items to be added.

· Index: Location index of the added item.

· Item: the value of the added item.

You can also use the PyList_GetItem () function in Python/c api to obtain the value of an item in the list. The value returned by the PyList_GetItem () function. The function prototype is as follows.

PyObject * PyList_GetItem (PyObject * list, Py_ssize_t index)

The parameter meanings are as follows.

· List: list of operations to be performed.

· Index: index of the position of an item.

Python embedded in C/C ++) in the actual operation process, the Python/c api provides the function corresponding to the List Operation in Python. For example, the List append method corresponds to the PyList_Append () function. The sort method of the list corresponds to the PyList_Sort () function. The reverse Method of the list corresponds to the PyList_Reverse () function. The function prototype is as follows.

Int PyList_Append (PyObject * list, PyObject * item)

Int PyList_Sort (PyObject * list)

Int PyList_Reverse (PyObject * list)

For the PyList_Append () function, the parameter meanings are as follows.

· List: list of operations to be performed.

· Item: the item to participate in.

For PyList_Sort () and PyList_Reverse () functions, the parameter meanings are the same.

· List: list of operations to be performed.

The above is an introduction to Python embedded in C/C ++ at a lower level.