to the original listnot copy of the list an unending stream of [ [ [ [ and so onuntil you hit the break-key combination on your machine (whichtechnicallyraises keyboardinterrupt exception that prints default messagebeginning with python the printer is clever enough to detect cycles and prints []instead to let you know that it has detected loop in the object' structure and avoided getting stuck printing forever the reason for the cycle is subtle and requires information you will glean in part iiso this is something of preview but in shortassignments in python always generate references to objectsnot copies of them you can think of objects as chunks of memory and of references as implicitly followed pointers when you run the first assignment abovethe name becomes named reference to two-item list object-- pointer to piece of memory python lists are really arrays of object referenceswith an append method that changes the array in place by tacking on another object reference at the end herethe append call adds reference to the front of at the end of lwhich leads to the cycle illustrated in figure - pointer at the end of the list that points back to the front of the list besides being printed speciallyas you'll learn in cyclic objects must also be handled specially by python' garbage collectoror their space will remain unreclaimed even when they are no longer in use though rare in practicein some programs that traverse arbitrary objects or structures you might have to detect such cycles yourself by keeping track of where you've been to avoid looping believe it or notcyclic data structures can sometimes be usefuldespite their special-case printing part iitypes and operations see "test your knowledgepart ii exerciseson page in for the exercises part iitypes and operations