Entry

Inverting a dictionary

Jul 5th, 2000 09:59
Nathan Wallace, unknown unknown, Hans Nowak, Snippet 54, Guido van Rossum

"""
Packages: basic_datatypes.dictionaries
"""

"""
> Well -- there is Guido van Rossum's variant:

Here's the correct version:
"""

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