Python 3.0 - is this true?

Diez B. Roggisch deets at nospam.web.de
Sun Nov 9 16:17:46 CET 2008


Roy Smith schrieb:
> In article <6no8p6Fm8q70U1 at mid.uni-berlin.de>,
>  "Diez B. Roggisch" <deets at nospam.web.de> wrote:
> 
>>> Also, I thought that part of the python philosophy was to allow any
>>> sort of object in a list, and to allow the same methods to work with
>>> whatever was in list.
>> Not really. When the usual argument about the existence (and 
>> justification) of lists & tuples comes along, one common distinction is 
>> that
>>
>>   - tuples contain arbitrary object of varying types, so they are kind 
>> of "records"
>>   - lists should contain uniform objects.
> 
> I see absolutely nothing wrong with lists of heterogenous types.  Or, for 
> that matter, iterators which generate heterogeneous types.  Here's some 
> perfectly reasonable examples (equally applicable to lists or iterators):
> 
> * The tokens parsed out of a file (ints, floats, identifiers, keywords, 
> various kinds of punctuation, etc)
> 
> * The entries in a unix directory (plain files, directories, symlinks, 
> special files, named sockets, etc)
> 
> * The vehicles going through a toll booth (cars, trucks, motorcycles)
> 
> I don't see any reason you shouldn't be able to build lists of those things.

When I wrote "uniform" I meant objects of the same kind. So for example 
subclasses are of course ok. And all of your examples are these: I want 
a Token-object, keeping file-location and possibly original string 
representation. The same goes for files - they are simply strings, their 
properties determined using stat-calls. And vehicles are... vehicles. So 
I'd create a common base-class for them, or made them at least behave 
proper through duck-typing. Which - for the case at hand - might include 
creating a __cmp__-method, based on horsepower or price-tag or...

Diez



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