[EMAIL PROTECTED] said unto the world upon 12/01/06 03:15 AM:
> I can think of several messy ways of making a dict that sets a flag if
> it's been altered, but I have a hunch that experienced python
> programmers would probably have an easier (well maybe more Pythonic)
> way of doing this.
>
> It's important that I can read the contents of the dict without
> flagging it as modified, but I want it to set the flag the moment I add
> a new element or alter an existing one (the values in the dict are
> mutable), this is what makes it difficult. Because the values are
> mutable I don't think you can tell the difference between a read and a
> write without making some sort of wrapper around them.
>
> Still, I'd love to hear how you guys would do it.
>
> Thanks,
> -Sandra
>
Hi Sandra,
here's one attempt. (I'm no expert, so wait for better :-)
>>> class ModFlagDict(dict):
def __init__(self, *args, **kwargs):
super(ModFlagDict, self).__init__(*args, **kwargs)
self.modified = False
def __setitem__(self, key, value):
self.modified = True
super(ModFlagDict, self).__setitem__(key, value)
>>> md = ModFlagDict(a=4, b=5)
>>> md
{'a': 4, 'b': 5}
>>> md.modified
False
>>> md[3]=5
>>> md
{'a': 4, 3: 5, 'b': 5}
>>> md.modified
True
>>>
It's broken in at least one way:
>>> newmd = ModFlagDict(3=4, 1=5)
SyntaxError: keyword can't be an expression
>>>
So, as it stands, no integers, floats, tuples, etc can be keys on
initialization. I think that can be be worked around by catching the
exceptions and setting the desired key-value pairs that way. But, it
is almost 4am, and I also suspect there is a much better way I am not
thinking of :-)
Best,
Brian vdB
--
http://mail.python.org/mailman/listinfo/python-list
