The little source code on the following web page 
demonstrates outdated patterns:

http://python.org/doc/Introduction.html

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

Perhaps the following would be cleaner:

def invert(table):
    index = {}                # empty dictionary
    for key in table: #"for key, value in table.iteritems():"?
        value = table[key]
        if value not in index:
            index[value] = [] # empty list
        index[value].append(key)
    return index

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I fail to see the problem. The code is not outdated, it
continues to work just fine. As for clarity, I find explicit
usage of .keys() and .has_key() clearer than with your
proposed change. Explicit is better than implicit.

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Martin's right; there's no clear reason to make the
suggested change.  Closing the report.