subclassing collections.Counter

[Pavlos Parissis]

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

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