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

[Shane Holloway (IEEE)]

Raymond Hettinger wrote:
> I would think that that generic clearing is a lark.  First, it only
> applies to mutable objects.  Second, it would likely only be useful in
> the presence of a generic method for adding to the cleared container (as
> opposed to the existing append(), add(), and setitem() methods for
> lists, sets, and dictionaries respectively).  So, for lists, stick with
> the current idiom:
> 
>    mylist[:] = []       # clear

Pros of list.clear:
 + easy to find in documentation and help()
 + readability & clarity of intention in code
 + commonality with other mutable collections
 + easier to search on "clear()" (well, at least for me...)

Cons of list.clear:
 + Yet another method on list
 + Three ways to do the same thing.
     mylist[:] = []
     del mylist[:]
     mylist.clear()

     (Although the implementation will use one of slice operators,
so I guess that depends on how you count ;)


I would agree generic clearing is a lark in terms of programming
feature.  However, I have been asked how to clear a list more than a
handful of times.  Personally, my opinion is that having a
list.clear method would be a net win, especially since the
implementation can be implemented via __setitem__ or __delitem__.

Are there more Cons than those I have listed?