Glenn Linderman <[EMAIL PROTECTED]> writes:
> On approximately 11/23/2008 1:40 AM, came the following characters
> from the keyboard of Steven D'Aprano:
>> On Sun, 23 Nov 2008 01:18:17 -0800, bearophileHUGS wrote
>>> Stef Mientki:
>>>
>>>> I would like to detect if a dictionary has been changed. So I would
>>>> like to have a modified-flag.
>>>>
>>> A solution is of course to create a SDict class, that works like a
>>> normal dict, and also watches for changes and has an extra boolean
>>> attribute.
>>>
>>
>> What does the S stand for?
>>
>> Untested and possibly incomplete:
>>
>> def factory(methodname, cls=dict, flag=True):
>> def method(self, *args, **kwargs):
>> self.modified = flag
>> return getattr(cls, methodname)(self, *args, **kwargs)
>> return method
>>
>>
>> class SDict(dict):
>> __init__ = factory('__init__', flag=False)
>> __setitem__ = factory('__setitem__')
>> __delitem__ = factory('__delitem__')
>> clear = factory('clear')
>> pop = factory('pop')
>> popitem = factory('popitem')
>> setdefault = factory('setdefault')
>> update = factory('update')
>>
>
> Interesting technique. I must point out, though, that it doesn't
> indicate if a dict has been changed, only that potentially changing
> operations have been performed. So it really depends on what Stef
> originally meant by changed, and perhaps what is meant by == :)
>
> x = {'a', 3}
You mean x = {'a': 3}!
> x['a'] = 3
>
> Whether x has been changed by the second statement is the open
> question. The above code would declare it has, but most people, when
> shown before and after copies of the dict, with declare it hasn't.
Good point. What about
>>> d = {1: []}
>>> d[1].append(2)
Has d changed or not?
--
Arnaud
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