subclassing collections.Counter

[Pavlos Parissis]

On 15/12/2015 05:18 μμ, Pavlos Parissis wrote:
> On 15/12/2015 05:08 μμ, Peter Otten wrote:
>> Pavlos Parissis wrote:
>>
>>> 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: maximum
>>> recursion depth exceeded as I access an attribute inside
>>> __getitem__.
>>>
>>> Does anyone has an idea how I can achieve this?
>>
>>> class CounterExt(Counter):
>>
>>>     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]
>>
>> self[key] will call the CounterExt.__getitem__() method again. Use 
>> super().__getitem__(key) instead to invoke Counter.__getitem__().
>>
>>
>>
> 
> 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
> 

Calling items() over the object doesn't call __getitem__ and I can't
find in the doc which method I need to change, any ideas?

Cheers,
Pavlos

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