Delete dict and subdict items of some name

MRAB python at mrabarnett.plus.com
Tue Dec 18 00:08:23 CET 2012


On 2012-12-17 22:00, Dave Angel wrote:
> On 12/17/2012 04:33 PM, Mitya Sirenef wrote:
>> On 12/17/2012 01:30 PM, Tim Chase wrote:
>>> On 12/17/12 11:43, Mitya Sirenef wrote:
>>>> On 12/17/2012 12:27 PM, Gnarlodious wrote:
>>>>> Hello. What I want to do is delete every dictionary key/value
>>>>> of the name 'Favicon' regardless of depth in subdicts, of which
>>>>> there are many. What is the best way to do it?
>>>> Something like this should work:
>>>>
>>>> def delkey(d, key):
>>>>       if isinstance(d, dict):
>>>>           if key in d: del d[key]
>>>>           for val in d.values():
>>>>               delkey(val, key)
>>> Unless you have something hatefully recursive like
>>>
>>>    d = {}
>>>    d["hello"] = d
>>>
>>> :-)
>>
>> True -- didn't think of that..!
>>
>> I guess then adding a check 'if val is not d: delkey(val, key)'
>> would take care of it?
>>
> No, that would only cover the self-recursive case.  If there's a dict
> which contains another one, which contains the first, then the recursion
> is indirect, and much harder to check for.
>
> Checking reliably for arbitrary recursion patterns is tricky, but
> do-able.  Most people degenerate into just setting an arbitrary max
> depth.  But I can describe two approaches to this kind of problem.
>
Wouldn't a set of the id of the visited objects work?



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