the third line does not change the int object the result of the addition operation refers to different object and the name is assigned to ithence is still associated with the integer no conflict it is not technically correct to think of as being the number and then but little sloppiness of thought does not get you in trouble with immutable types with mutable typeshoweverbe very careful of aliases then it is very important to remember the indirectnessthat name is not the same thing as the object it refers to another mutable type is list list can be cloned with the slice notation[:try the following in the shell nums [ numsalias nums numsclone nums[:nums append( numsalias append( nums numsalias numsclone animation run the example programbackandforth py the whole program is shown below for convenience then each individual new part of the code is discussed individually'''test animation and depth ''from graphics import import time actuallylists are even trickierbecause individual elements of list may be mutableeach mutable element in the cloned list is an alias of the corresponding element in the original listso if you mutate its state in the cloned listyou also make change to the original list this is distinct from the situation if you replace an element in the cloned list by totally different onethen you do not change the original list objects and methods