[Tutor] Where to put small auxiliary function

[Joel Goldstick]

On Fri, Jul 20, 2012 at 6:32 AM, Mark Lawrence <breamoreboy at yahoo.co.uk> wrote:
> On 20/07/2012 11:07, Jose Amoreira wrote:
>>
>> Hi.
>> This is a question about style. I have a class definition that calls a
>> small auxiliary function. Because this function isn't used anywhere
>> else, I'd like to include it inside the class definition. However, if
>> I do that, I'll have to use "self" in the call argument, which is (I
>> think) rather awkward.
>> Let me give an example:
>>
>> def is_odd(k):
>>      if k % 2 == 0:
>>          return False
>>      else:
>>          return True
>
>
> I'll point out before anyone else does that you can write this function as a
> one line return.  I'll leave you to work out how.  Personally I prefer the
> longer version but each to their own.

I like return k % 2


>
>
>>
>> class MyOddNbr(object):
>>      def __init__(self, k):
>>          if is_odd(k):
>>              self.k = k
>>          else:
>>              self.k = k + 1

   class MyOddNbr(object):
         def __init__(self, k):
             self.k = k + k % 2


>>
>> This works fine, but I'd like to have is_odd defined inside the class
>> definition, because that's the only context where that function is
>> used. That would be something like
>>
>> class MyOddNbr(object):
>>      def is_odd(self,k):
>>          if k % 2 == 0:
>>              return False
>>          else:
>>              return True
>>      def __init__(self,k):
>>          if self.is_odd(k):
>>              self.k = k
>>          else:
>>              self.k = k + 1
>>
>> This also works fine, but the function is_odd() is so simple and
>> generic that I find it strange to define it with is_odd(self,k) or to
>> call it with is_odd(self,k).
>> What is the pythonic way of doing this kind of stuff?
>
>
> Don't put it in the class.  It's a general purpose function that can be used
> anywhere so keep it at the module level.
>
>
>> Thanks.
>> Ze
>> _______________________________________________
>> Tutor maillist  -  Tutor at python.org
>> To unsubscribe or change subscription options:
>> http://mail.python.org/mailman/listinfo/tutor
>>
>
>
> --
> Cheers.
>
> Mark Lawrence.
>
>
>
>
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor



-- 
Joel Goldstick