dictionaries the order of the key-value pairs is not the same in factif you type the same example on your computeryou might get different result in generalthe order of items in dictionary is unpredictable but that' not problem because the elements of dictionary are never indexed with integer indices insteadyou use the keys to look up the corresponding valuesprint(eng sp['two']'dosthe key 'twoalways maps to the value "dosso the order of the items doesn' matter if the key isn' in the dictionaryyou get an exceptionprint(eng sp['four']keyerror'fourthe len function works on dictionariesit returns the number of key-value pairslen(eng sp the in operator works on dictionariesit tells you whether something appears as key in the dictionary (appearing as value is not good enough'onein eng sp true 'unoin eng sp false to see whether something appears as value in dictionaryyou can use the method valueswhich returns the values as type that can be converted to listand then use the in operatorvals list(eng sp values()'unoin vals true the in operator uses different algorithms for lists and dictionaries for listsit uses linear search algorithm as the list gets longerthe search time gets longer in direct proportion to the length of the list for dictionariespython uses an algorithm called hash table that has remarkable propertythe in operator takes about the same amount of time no matter how many items there are in dictionary won' explain why hash functions are so magicalbut you can read more about it at wikipedia org/wiki/hash_table exercise download copy of the file www py com/code /words txt write program that reads the words in words txt and stores them as keys in dictionary it doesn' matter what the values are then you can use the in operator as fast way to check whether string is in the dictionary