Extending Python's dictionary

LongNameDict.py

class LongNameDict(dict):
    def longest_value(self):
        longest = None
        for key, value in self.items():
            if not longest or len(value) > len(longest):
                longest = value
        return longest

names = LongNameDict(first='josé', second='schwarzenegger')

assert names.longest_value() == 'schwarzenegger'
assert not names.longest_value() == 'josé'