Python and C++ integration

I'm trying to do integrate with python and c++ now and what I'm gonna do is using c++ function in python.

The feature of function is read all text in a text file.

I know I have to make c++ code to c style, so I made c++ code like below:

void ReadTextFile(string fileName)
{
    string str;
    string line;
    
    ifstream file(fileName);
    while(getline(file, line))
    {
        vector<string> result = split(line, ':');
        if (result.size() > 1)
        {
            result[1].erase(std::remove(result[1].begin(), result[1].end(), ' '), result[1].end());
            cout << result[1] << endl;
        }
    }
}



extern "C" {
    void ReadTextFileCpp(string fileName) {return ReadTextFile(fileName);
}

So I can get right result what I want to when I just build this c++ file.

But the problem is when I build this cpp file to .so file and call this function in python file. this is what I call the function in python:

lib2 = cdll.LoadLibrary('./ReadTextFile.so')
lib2.ReadTextFileCpp('0166_405504.txt')

The error occurs when I call the ReadTextFile function and this is the error message.

terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

Why this error occurs only when I call in python?

p.s) I have changed 'std::string' to 'const char*'. This code runs but it doesn't get inside of while loop.

void ReadTextFile(const char* fileName)
{
    string str;
    string line;
    
    ifstream file(fileName);
    while(getline(file, line))
    {
        vector<string> result = split(line, ':');
        if (result.size() > 1)
        {
            result[1].erase(std::remove(result[1].begin(), result[1].end(), ' '), result[1].end());
            cout << result[1] << endl;
        }
    }
}



extern "C" {
    void ReadTextFileCpp(const char* fileName) {return ReadTextFile(fileName);
}