sets and maps instead of using two lists to store the key/value entries in the mapwe can use single list the individual keys and corresponding values can both be saved in single objectwith that object then stored in the list sample instance illustrating the data organization required for this approach is shown in figure entrylist map mapentry smith smith john john east east main main st st somewhere somewhere va va smith smith jane jane jefferson jefferson st st east east end end pa pa roberts roberts susan susan quarry quarry rd rd nowhere nowhere tx tx brown brown jessica jessica quarry quarry rd rd plains plains tn tn figure the map adt implemented using single list the implementation of the map adt using single list is provided in listing as we indicated earlier in we want to avoid the use of tuples when storing structured data since it' better practice to use classes with named fields the mapentry storage classdefined in lines - will be used to store the individual key/value pairs note this storage class is defined to be private since it' only intended for use by the map class that provides the single list implementation of the map adt listing the linearmap py module implementation of map adt using single list class map creates an empty map instance def __init__self )self _entrylist list(returns the number of entries in the map def __len__self )return lenself _entrylist determines if the map contains the given key def __contains__selfkey )ndx self _findpositionkey return ndx is not none adds new entry to the map if the key does exist otherwisethe