staticPyMutexmu;staticPyObject*mymodule=nullptr;// It is important that we use a critical section here rather than a regular// PyMutex, say 'M', because we need to avoid the following deadlock:// * thread T1 holds M and calls ImportModule, which attempts to acquire a//   critical section C.// * thread T2 holds critical section C and attempts to call this code and//   acquire M.// In general, if you're going to hold a lock while calling into Python code, it had better be a critical section.PyCriticalSectioncs;_PyCriticalSection_BeginMutex(&cs,&mu);if (!mymodule) {PyObject*m=PyImport_ImportModule("mymodule");// Importing may have released the critical section, so it is possible// another thread might have populated mymodule. Make sure we clean up after// ourselves in that case.std::swap(mymodule,m);Py_XDECREF(m);}PyCriticalSection_End(&cs);

staticPyObjectobject_for_mu;// Not really an object, we just want its mutex.staticPyObject*mymodule=nullptr;PyCriticalSectioncs;PyCriticalSection_Begin(&cs,&object_for_mu);if (!mymodule) {PyObject*m=PyImport_ImportModule("mymodule");std::swap(mymodule,m);Py_XDECREF(m);}PyCriticalSection_End(&cs);