as more striking exampleit is common practice in python to initialize an array of integers using syntax such as counters [ this syntax produces list of length eightwith all eight elements being the value zero technicallyall eight cells of the list reference the same objectas portrayed in figure counters figure the result of the command data [ at first glancethe extreme level of aliasing in this configuration may seem alarming howeverwe rely on the fact that the referenced integer is immutable even command such as counters[ + does not technically change the value of the existing integer instance this computes new integerwith value and sets cell to reference the newly computed value the resulting configuration is shown in figure counters figure the result of command data[ + upon the list from figure as final manifestation of the referential nature of listswe note that the extend command is used to add all elements from one list to the end of another list the extended list does not receive copies of those elementsit receives references to those elements figure portrays the effect of call to extend extras primes figure the effect of command primes extend(extras)shown in light gray