How to change behavior of dict() for an instance

Question

So I\'m writing a class that extends a dictionary which right now uses a method \"dictify\" to transform itself into a dict. What I would like to do instead though is change it

Answer 1

Nothing wrong with your approach, but this is similar to the Autovivification feature of Perl, which has been implemented in Python in this question. Props to @nosklo for this.

class RecursiveDict(dict):
    """Implementation of perl's autovivification feature."""
    def __getitem__(self, item):
        try:
            return dict.__getitem__(self, item)
        except KeyError:
            value = self[item] = type(self)()
            return value

>>> a = RecursiveDict()
>>> a[1][2][3] = 4
>>> dict(a)
{1: {2: {3: 4}}}

EDIT

As suggested by @Rosh Oxymoron, using __missing__ results in a more concise implementation. Requires Python >= 2.5

class RecursiveDict(dict):
    """Implementation of perl's autovivification feature."""
    def __missing__(self, key):
        value = self[key] = type(self)()
        return value