[Tutor] Re: How do you share a method (function) among several objects?

[Pierre Barbier de Reuille]

The position to put it is a design choice and there is no single best 
solution. What I'd do is to gather all the small "homeless" functions in 
a single separate module. And if they come to be too numerous, I'll sort 
them in some modules, ...

But that's because I don't like having a single function in a module ^_^
Of course, if this is a complex function, that can make sense ...

I hope I helped and didn't make things worst ;)

Pierre

Xif a écrit :
> Ok, so keeping getCells() as an external function makes sense.
> 
> But where exactly do you recommend I'd put it?
> 
> In a seperate module, like I currently do, even though it's going to be 
> the only piece of code contained inside that module?
> 
> Xif
> 
> Pierre Barbier de Reuille wrote:
> 
>> Well, for me, the more logical answer is : multi-inheritance !
>> If part of your class is the same, (same semantic, same 
>> implementation), then you want to have a base class for that.
>>
>> If you dislike this kindof inheritance, then your function should be 
>> an external one. Even more because it's 'just' an implementation 
>> function. The user don't need it as a method ... So why bother add it 
>> to your object ?
>>
>> Pierre
>>
>> Xif a יcrit :
>>
>>> Javier Ruere wrote:
>>>
>>>> Xif wrote:
>>>>
>>>>> Hello
>>>>>
>>>>> There are several different objects. However, they all share the same
>>>>> function.
>>>>>
>>>>> Since they are not the same or similar, it's not logical to use a
>>>>> common superclass.
>>>>>
>>>>> So I'm asking, what's a good way to allow those objects to share that
>>>>> function?
>>>>>
>>>>> The best solution I've found so far is to put that function in a
>>>>> module, and have all objects import and use it. But I doubt that's a
>>>>> good use-case for modules; writing and importing a module that 
>>>>> contains
>>>>> just a single function seems like an abuse.
>>>>>
>>>>> Thanks,
>>>>> Xif
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>   Could you give an example?
>>>>
>>>> Javier
>>>>
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>>>>
>>> Sure, I can describe my particular case.
>>>
>>> It's a program that retrieves / updates Microsoft Excel spreadsheet 
>>> data.
>>>
>>> There are two major classes:
>>>
>>> 1) an Excel class, that represents of the whole Excel program
>>> 2) a Cells class, that abstracts retrieval  and editing of cells.
>>>
>>> Both classes use a function called getCells() as part of their 
>>> __getitem__() methods.
>>>
>>> getCells() parses the __getitem__() call arguments, and returns an 
>>> iterator over the appropriate cells.
>>>
>>> The difference between the 2 classes is that a Cells instance just 
>>> converts the generator into a list and returns it:
>>>
>>> #<code>
>>> return list(getCells(self.sheet, cells))
>>> #</code>
>>>
>>> while an Excel instance returns the values of the cells:
>>>
>>> #<code>
>>> return [cell.Value for cell in getCells(self.sheet, cells)]
>>> #</code>
>>>
>>> As you can see, both use the getCells() function.
>>>
>>> So my question is, where is the best way to put it so instances of 
>>> both classes can use it?
>>>
>>> Xif
>>> _______________________________________________
>>> Tutor maillist  -  Tutor at python.org
>>> http://mail.python.org/mailman/listinfo/tutor
>>>
>>
> 

-- 
Pierre Barbier de Reuille

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