tuples, index method, Python's design

Duncan Booth duncan.booth at invalid.invalid
Tue Apr 10 14:40:30 CEST 2007


Antoon Pardon <apardon at forel.vub.ac.be> wrote:

> On 2007-04-10, Duncan Booth <duncan.booth at invalid.invalid> wrote:
>> There is a cost to every new language feature: it has to be
>> implemented, documented, maintained, and above all learned by the
>> users. Good design involves, in part, not adding to these burdens
>> except where there is a benefit at least equal to the cost.
> 
> So what is the easiest to learn: "All sequences have an index method"
> or "Such and so sequences have an index method and others don't"
> 
> Which of the above is the easiest to document?

The second would be if it were true. However it would mean you would have 
to add an index method to *all* sequences.

FWIW, The current documentation says that 's.index' is a method defined on 
all *mutable* sequence types: almost as simple as your second wording but 
unfortunately misleading since strings also have index.

> If someone states: "Show me your use case for using tuple.index and I
> will show you how to avoid it." or words to that effect I think there
> is little use trying.

I genuinely cannot think of a use case. I didn't ask you to suggest one so 
I could show you how to avoid it, I asked you to suggest one so that we 
could take the discussion from the purely hypothetical to a more concrete 
discussion of whether it would be a worthwhile enhancement.

Fair enough though. I'll assume you cannot think of a suitable use case 
either.



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