The Python Programming Language

Description

Source Code

>>> def invert(table):		
...index = { }				#empty dictionary
...for key in table.keys():
......value = table[key]
......if not index.has_key(value):
.........index[value] = []			# empty list
......index[value].append(key)
...return index

Sample Run

>>> phonebook() = {'guido': 4127, 'sjoerd': 4127, 'jack' : 4098}
>>> phonebook['dcab'] = 4147
>>> inverted_phonebook = invert(phonebook)
>>> print inverted_phonebook
{ 4098: ['jack'], 4127: ['guido', 'sjoerd'], 4147: ['dcab'] }