我在从C++调用一个简单的Python脚本时遇到了问题。
我有一个简单的用例来说明这个问题；
在Python脚本中，函数fb应该调用已事先定义好的fa。

然而我却得到一个错误：

调用了fb

Traceback (most recent call last):
    File "<string>", line 1, in <module>
    File "<string>", line 13, in <module>
    File "<string>", line 10, in fb
NameError: name 'fa' is not defined

文件test.py：

def fa() :
       print('Called fa')
       return 3
def fb() :
       print('Called fb')
       return fa() * 2
fb()
print('Finished test.py')

C++代码：

#ifdef _DEBUG
#undef _DEBUG
#include <Python.h>
#define _DEBUG
#else
#include <Python.h>
#endif
#include <string>
int main() {

    // Initialize the python interpreter, setting path
    const char * app_path = "C:\\Python383-x64\\";
    size_t convertedChars = 0;
    size_t newsize = strlen(app_path);
    wchar_t* wcstring = new wchar_t[newsize];
    mbstowcs_s(&convertedChars, wcstring, newsize, app_path, _TRUNCATE);
    Py_SetPythonHome(wcstring);
    Py_Initialize();

    // Create dicts for globals and locals
    PyObject* globals = PyDict_New();
    PyObject* locals = PyDict_New();

    // Set the builtins
    PyDict_SetItemString(globals, "__builtins__", PyEval_GetBuiltins());

    // Evaluate python code and get the result
    PyObject* string_result = PyRun_String("exec(open(\"test.py\").read())",     Py_single_input, globals, locals);

    // check whether the python code caused any Exception
    if (PyErr_Occurred()) {
        PyErr_Print(); PyErr_Clear(); return 1;
    }
    else {
        // print the result
        PyObject_Print(string_result, stdout, Py_PRINT_RAW);
    }
    return 0;
}

解决方案

因此，答案是在字典中添加 __main__。

#ifdef _DEBUG
#undef _DEBUG
#include <Python.h>
#define _DEBUG
#else
#include <Python.h>
#endif
#include <string>
int main() {

    // Initialize the python interpreter, setting path
    const char * app_path = "C:\\Python383-x64\\";
    size_t convertedChars = 0;
    size_t newsize = strlen(app_path);
    wchar_t* wcstring = new wchar_t[newsize];
    mbstowcs_s(&convertedChars, wcstring, newsize, app_path, _TRUNCATE);
    Py_SetPythonHome(wcstring);
    Py_Initialize();

    // Create dicts for globals and locals
    PyObject* main_module = PyImport_AddModule("__main__");
    PyObject* locals = PyModule_GetDict(main_module);
    PyObject* globals = PyModule_GetDict(main_module);
    PyDict_SetItemString(globals, "__builtins__", PyEval_GetBuiltins());

    // Evaluate python code and get the result
    PyObject* string_result = PyRun_String("exec(open(\"test.py\").read())", Py_file_input, globals, locals);

    // check whether the python code caused any Exception
    if (PyErr_Occurred()) {
        PyErr_Print(); PyErr_Clear(); return 1;
    }
    return 0;
}