Entry

Bi-directional dictionary

Jul 5th, 2000 10:01
Nathan Wallace, unknown unknown, Hans Nowak, Snippet 186, Stephan Houben

"""
Packages: basic_datatypes.dictionaries
"""

# bidict.py
""" A bidirectional dictionary, based on code posted to the Python ML, by
Stephan Houben."""

from UserDict import UserDict

class BiDict(UserDict):

    def __getitem__(self, item):
        return self.data[item]

    def __setitem__(self, item, value):
        self.__erase(item)
        self.__erase(value)

        self.data[item] = value
        self.data[value] = item

    def __delitem__(self, item):
        del self.data[self.data[item]]
        #the second item is already be erased iff item == self.data[item]
        try:
            del self.data[item]
        except KeyError:
            pass	

    #try to delete an item	
    def __erase(self, item):	
        try:
            del self.data[self.data[item]]
        except KeyError:
            pass	    

    def __repr__(self):
        return repr(self.data)		


if __name__ == '__main__':

    test = BiDict()

    test['a'] = 'b'
    test['c'] = 'd'  
    print 'test =', test

    test['b'] = 'c'    
    print 'test =', test

    test['c'] = 'c'
    print 'test =', test

    del test['c']
    print 'test =', test