将 python 嵌入到 C++ 中

Question

I am a bit confused for my implementation. I have a python script to be embedded into C++.

import urllib.request
import ssl
import suds.transport.http
from suds.client import Client

class UnverifiedHttpsTransport(suds.transport.http.HttpTransport):
  def __init__(self, *args, **kwargs):
     super(UnverifiedHttpsTransport, self).__init__(*args, **kwargs)
  def u2handlers(self):
     handlers = super(UnverifiedHttpsTransport, self).u2handlers()
     context = ssl.create_default_context()
     context.check_hostname = False
     context.verify_mode = ssl.CERT_NONE
     handlers.append(urllib.request.HTTPSHandler(context=context))
     return handlers

url="https://xxxxxest.com/datamanagement.asmx?WSDL"
client = Client(url, transport=UnverifiedHttpsTransport())

def ReadDataTest():
  result = client.service.ReadTestData()
  return result

def ReadGridData():
  result = client.service.ReadGridData()  
  return result

def main():
  result=ReadGridData()
  print(result)

if __name__ == "__main__":
  main()

Then sample_main.cpp has plugin lib sample_plugin.cpp.

sample_plugin.cpp has python embedded code as follows.

  Py_Initialize();
  pName = PyUnicode_DecodeFSDefault("web_interface");
  pModule = PyImport_Import(pName);
  Py_DECREF(pName);
  if (pModule != NULL) {
    pFunc_readtest = PyObject_GetAttrString(pModule, "ReadDataTest");
    if (pFunc_readtest && PyCallable_Check(pFunc_readtest)) {
      pValue = PyObject_CallObject(pFunc_readtest, NULL);
      if(pValue != NULL) {
         printf("Result of call: %s\n", pValue);
         Py_DECREF(pValue);
      }
    }
    Py_XDECREF(pFunc_readtest);
    Py_DECREF(pModule);
  }else{
    PyErr_Print();
    printf("Can't call python \n");
  }
  Py_FinalizeEx();

When I run sample_main.exe, I have errors as

Traceback (most recent call last):
  File "/opt/nvidia/deepstream/deepstream-5.0/sources/apps/sample_apps/deepstream-test3/web_interface.py", line 2, in <module>
    import ssl
  File "/usr/lib/python3.6/ssl.py", line 101, in <module>
    import _ssl             # if we can't import it, let the error propagate
ImportError: /usr/lib/python3.6/lib-dynload/_ssl.cpython-36m-aarch64-linux-gnu.so: undefined symbol: PyExc_OSError
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
    from apport.report import Report
  File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in <module>
    import apport.fileutils
  File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in <module>
    from apport.packaging_impl import impl as packaging
  File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 24, in <module>
    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
    import apt_pkg
ImportError: /usr/lib/python3/dist-packages/apt_pkg.cpython-36m-aarch64-linux-gnu.so: undefined symbol: PyExc_ValueError

Original exception was:
Traceback (most recent call last):
  File "/opt/nvidia/deepstream/deepstream-5.0/sources/apps/sample_apps/deepstream-test3/web_interface.py", line 2, in <module>
    import ssl
  File "/usr/lib/python3.6/ssl.py", line 101, in <module>
    import _ssl             # if we can't import it, let the error propagate
ImportError: /usr/lib/python3.6/lib-dynload/_ssl.cpython-36m-aarch64-linux-gnu.so: undefined symbol: PyExc_OSError

The error is removed when I include Py_Initialize(); inside sample_main.cpp .

Can somebody explain why it is necessary to include Py_Initialize(); inside sample_main.cpp ?

Is that the right way to do that? What are the things I need to care inside

sample_main.cpp

for memory leak or anything other issues?

Answer 1

In an application embedding Python, the Py_Initialize() function must be called before using any other Python/C API functions

First words of the documentation, https://docs.python.org/3/c-api/init.html