Entry

Weak dictionary

Jul 5th, 2000 10:00
Nathan Wallace, unknown unknown, Hans Nowak, Snippet 145, Python Snippet Support Team

"""
Packages: basic_datatypes.dictionaries
"""

# weakdict.py
# It is *very* easy to make a weak dictionary in Python... This is a simple
# example.

# HN, 23 Nov 98

from UserDict import UserDict

class WeakDict(UserDict):
    def __setitem__(self, name, value):
        self.data[name] = value
        if not value:
            del self.data[name]


if __name__ == "__main__":

    wd = WeakDict()
    wd['hans'] = 25
    wd['anjo'] = 22
    wd['mari'] = 35
    wd['fred'] = 33
    print wd

    wd['fred'] = None   # this deletes the 'fred' entry
    print wd