maps and dictionaries python' dict class is arguably the most significant data structure in the language it represents an abstraction known as dictionary in which unique keys are mapped to associated values because of the relationship they express between keys and valuesdictionaries are commonly known as associative arrays or maps in this bookwe use the term dictionary when specifically discussing python' dict classand the term map when discussing the more general notion of the abstract data type as simple examplefigure illustrates map from the names of countries to their associated units of currency turkey lira spain greece euro china united states india yuan dollar rupee figure map from countries (the keysto their units of currency (the valueswe note that the keys (the country namesare assumed to be uniquebut the values (the currency unitsare not necessarily unique for examplewe note that spain and greece both use the euro for currency maps use an array-like syntax for indexingsuch as currencygreece to access value associated with given key or currencygreece drachma to remap it to new value unlike standard arrayindices for map need not be consecutive nor even numeric common applications of maps include the following university' information system relies on some form of student id as key that is mapped to that student' associated record (such as the student' nameaddressand course gradesserving as the value the domain-name system (dnsmaps host namesuch as www wiley comto an internet-protocol (ipaddresssuch as social media site typically relies on (nonnumericusername as key that can be efficiently mapped to particular user' associated information computer graphics system may map color namesuch as turquoise to the triple of numbers that describes the color' rgb (red-green-bluerepresentationsuch as ( , , python uses dictionary to represent each namespacemapping an identifying stringsuch as pi to an associated objectsuch as in this and the next we demonstrate that map may be implemented so that search for keyand its associated valuecan be performed very efficientlythereby supporting fast lookup in such applications