By default, PyMongo correctly calls the "insert" command with no writeConcern, and calls getLastError with no "w" argument.
But PyMongo should include writeConcern of "w=1" with the insert command, or call getLastError with "w=1", if configured like this:
Or if called like this:
The purpose of sending w=1 is to override getLastErrorDefaults. Since getLastErrorDefaults are rarely, if ever, configured, this is a low-priority bug.