contents of an address is constant-time operationthe question becomes whether we can compute the address of the ith element of list in constant time let' start by considering the simple case where each element of the list is an integer this implies that each element of the list is the same sizee four units of memory (four eight-bit bytes in this case the address in memory of the ith element of the list is simply start iwhere start is the address of the start of the list therefore we can assume that python could compute the address of the ith element of list of integers in constant time of coursewe know that python lists can contain objects of types other than intand that the same list can contain objects of many different types and sizes you might think that this would present problembut it does not in pythona list is represented as length (the number of objects in the listand sequence of fixed-size pointers to objects figure illustrates the use of these pointers the shaded region represents list containing four elements the leftmost shaded box contains pointer to an integer indicating the length of the list each of the other shaded boxes contains pointer to an object in the list figure implementing lists if the length field is four units of memoryand each pointer (addressoccupies four units of memorythe address of the ith element of the list is stored at the address start againthis address can be found in constant timeand then the value stored at that address can be used to access the ith element this access too is constant-time operation this example illustrates one of the most important implementation techniques used in computingindirection generally speakingindirection involves accessing something by first accessing something else that contains reference the number of bits used to store an integeroften called the word sizeis typically dictated by the hardware of the computer of size bits in some implementations and bits in others my dictionary defines "indirectionas "lack of straightforwardness and opennessdeceitfulness in factthe word generally had pejorative implication until about when computer scientists realized that it was the solution to many problems