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From: Pavlos Parissis <pavlos.parissis@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: subclassing collections.Counter
Date: Tue, 15 Dec 2015 17:18:31 +0100
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Message-ID: <mailman.30.1450196320.22044.python-list@python.org>
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On 15/12/2015 05:08 =CE=BC=CE=BC, Peter Otten wrote:
> Pavlos Parissis wrote:
>=20
>> I need to store values for metrics and return the average for some
>> and the sum for the rest. Thus, I thought I could extend
>> collections.Counter class by returning averages for some keys.
>>
>> My class modifies the update() to increment a counter and the
>> __getitem__ to perform the calculation. But, I get RuntimeError: maxim=
um
>> recursion depth exceeded as I access an attribute inside
>> __getitem__.
>>
>> Does anyone has an idea how I can achieve this?
>=20
>> class CounterExt(Counter):
>=20
>>     def __getitem__(self, key):
>>         if (self.avg_metrics is not None and key in self.avg_metrics):=

>>             return self[key] / self._counter
>>         else:
>>             return self[key]
>=20
> self[key] will call the CounterExt.__getitem__() method again. Use=20
> super().__getitem__(key) instead to invoke Counter.__getitem__().
>=20
>=20
>=20

I applied your suggestion and worked!
   def __getitem__(self, key):
        if (self.avg_metrics is not None and key in self.avg_metrics):
            return super().__getitem__(key) / self.__counter
        else:
            return super().__getitem__(key)

Thank you very much,
Pavlos


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