Track changes to lists and dictionaries in python?

Question

I have a class where the instances of this class needs to track the changes to its attributes.

Example: obj.att = 2 would be something that\'s easily tr

Answer 1

You could take advantage of the abstract base classes in the collections module, which dict and list implement. This gives you a standard library interface to code against with a short list of methods to override, __getitem__, __setitem__, __delitem__, insert. Wrap the attributes in a trackable adapter inside __getattribute__.

import collections

class Trackable(object):
    def __getattribute__(self, name):
        attr = object.__getattribute__(self, name)
        if isinstance(attr, collections.MutableSequence):
            attr = TrackableSequence(self, attr)
        if isinstance(attr, collections.MutableMapping):
            attr = TrackableMapping(self, attr)
        return attr

    def __setattr__(self, name, value):
        object.__setattr__(self, name, value)
        # add change tracking


class TrackableSequence(collections.MutableSequence):
    def __init__(self, tracker, trackee):
        self.tracker = tracker
        self.trackee = trackee

    # override all MutableSequence's abstract methods
    # override the the mutator abstract methods to include change tracking


class TrackableMapping(collections.MutableMapping):
    def __init__(self, tracker, trackee):
        self.tracker = tracker
        self.trackee = trackee

    # override all MutableMapping's abstract methods
    # override the the mutator abstract methods to include change tracking