Logging is done with the standard Python :pylogging module, and logging can be configured with the usual utilities. However, in the default build the debug logging is completely disabled for performance reasons1. To enable it, add -DSPEAD2_MAX_LOG_LEVEL=spead2::log_level::debug to the compiler options in setup.py.
Logging is done from separate C threads, which have to wait for Python's Global Interpreter Lock (GIL) in order to do logging.↩