So here’s my code: When I execute, I get TypeError: SubElement() argument 1 must be xml.etree.ElementTree.Element, not None What I need is to pass the value 20 (FLASHCMD_TIMEOUT) to the function op_sndrcv(). create_command() op_sndrcv() are used my multiple routines and I want to keep this as optional, without changing the current format, but just by introducing the new variable timeout