2.8 The UserDict Module

The UserDict module contains a dictionary class that can be subclassed (it's actually a Python wrapper for the built-in dictionary type).

Example 2-15 shows an enhanced dictionary class, which allows dictionaries to be "added" to each other and initialized using the keyword argument syntax.

Example 2-15. Using the UserDict Module

File: userdict-example-1.py

import UserDict

class FancyDict(UserDict.UserDict):

    def _ _init_ _(self, data = {}, **kw):
        UserDict.UserDict._ _init_ _(self)
        self.update(data)
        self.update(kw)

    def _ _add_ _(self, other):
        dict = FancyDict(self.data)
        dict.update(b)
        return dict

a = FancyDict(a = 1)
b = FancyDict(b = 2)

print a + b

{'b': 2, 'a': 1}