Think Python - Denison University

12.6. Dictionaries and tuples 119If you combine zip, for and tuple assignment, you get a useful idiom for traversing two (or more)sequences at the same time. For example, has_match takes two sequences, t1 and t2, and returnsTrueifthere isanindexisuch thatt1[i] == t2[i]:def has_match(t1, t2):for x, y in zip(t1, t2):if x == y:return Truereturn FalseIfyouneedtotraversetheelementsofasequenceandtheirindices,youcanusethebuilt-infunctionenumerate:for index, element in enumerate('abc'):print index, elementThe output of thisloop is:0 a1 b2 cAgain.12.6 Dictionariesand tuplesDictionarieshaveamethodcalleditemsthatreturnsalistoftuples,whereeachtupleisakey-valuepair 2 .>>> d = {'a':0, 'b':1, 'c':2}>>> t = d.items()>>> print t[('a', 0), ('c', 2), ('b', 1)]As you should expect from adictionary, the itemsareinno particular order.Conversely, you can usealistof tuples toinitializeanew dictionary:>>> t = [('a', 0), ('c', 2), ('b', 1)]>>> d = dict(t)>>> print d{'a': 0, 'c': 2, 'b': 1}Combiningdictwithzipyields aconcise way tocreate adictionary:>>> d = dict(zip('abc', range(3)))>>> print d{'a': 0, 'c': 2, 'b': 1}The dictionary method update also takes a list of tuples and adds them, as key-value pairs, to anexisting dictionary.Combining items, tuple assignment and for, you get the idiom for traversing the keys and valuesof adictionary:2 This behavioris slightly differentin Python3.0.