[Python-Dev] List copy and clear (was Re: Inconsistent API for sets.Set and build-in set)

[Nicolas Fleury]

Raymond Hettinger wrote:
> Several thoughts:

As I told you in a private dicussion, you have convinced me about copy. 
  About clear, however, I feel I have to defend my colleagues and 
myself, who almost all wasted time once (but only once) searching how to 
clear a list.  Improving the docs (like adding an additional example in 
the table at http://www.python.org/doc/2.4.1/lib/typesseq-mutable.html) 
would be good.  To me, "del mylist[:]" and "mylist[:] = []" are not "how 
to clear a list" but "how to clear list using slicing".  That's why I 
think it's counter-intuitive, since you end up using slicing in a 
situation that has nothing to do with slicing.

We agree there's no need about generic clearing.  It's only about 
consistency and ease of learning/self-documentation.  So let's look at 
the reasons to not do it:

- It's only useful for new Python programmers (I mean first-time 
clearers), once you know it, you know it.
- That would be a third way to clear a list.  However, I don't like this 
argument in this specific case, because IMO the current ways are just 
slicing capabilities, as "<< 1" and "* 2" can be the same on a int.
- All APIs trying to emulate a list would end up incomplete.  I have 
difficulty judging that one.  A method addition doesn't sound so bad to 
me.  If it is the showstopper, maybe a Python 3000 thing?

Overall, I think the addition of clear would be an improvement to the 
language, particularly in the autocompletion world of ours;)

Regards,
Nicolas