Bengt Richter wrote:
> You are right, but OTOH the OP speaks of a "flagging" the dict as
> modified. If she made e.g., "modified" a property of the dict
> subclass, then retrieving the the "modified" "flag" could dynamically
> check current state repr vs some prior state repr. Then the question
> becomes "modified w.r.t. what prior state?"
>
> This lets the OP ask at any time whether the dict is/has_been
> modified, but it's not a basis for e.g., a modification-event callback
> registry or such.
>
Good point. So the following matches what was asked for, although
depending on the actual use pattern it may or may not match what is
required:
---------- tracked.py -------------
import cPickle, md5
class TrackedDict(dict):
def __init__(self, *args, **kw):
dict.__init__(self, *args, **kw)
self.resetModified()
def __getstate__(self):
return dict(self)
def __setstate__(self, d):
self.update(d)
def _gethash(self):
pickle = cPickle.dumps(self)
hash = md5.new(pickle).digest()
return hash
@property
def modified(self):
return self._hash != self._gethash()
def resetModified(self):
self._hash = self._gethash()
if __name__=='__main__':
d = TrackedDict(x=[])
assert not d.modified
d['a'] = [1, 2, 3]
assert d.modified
d.resetModified()
assert not d.modified
d['a'].append(4)
assert d.modified
assert d== {'x':[], 'a':[1, 2, 3, 4]}
assert d==cPickle.loads(cPickle.dumps(d))
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