list.clear() missing?!?

[Duncan Booth]

Raymond Hettinger wrote:

> Cons:
> -----
> 
> * learning slices is basic to the language (this lesson shouldn't be
> skipped)
> 
also, a clear method would simply clear the entire list. You still need to 
learn the assigning to/deleting slices technique any time you want to clear 
out part of a list.

Every so often I still get an "oh, I didn't know Python could do *that* 
moment", just had one now:

>>> s = range(10)
>>> s[::2] = reversed(s[::2])
>>> s
[8, 1, 6, 3, 4, 5, 2, 7, 0, 9]

I've no idea when I might need it, but it just never occurred to me before 
that you can also assign/del non-contiguous slices.

The symmetry does breaks down a bit here as assigning to an extended slice 
only lets you assign a sequence of the same length as the slice, so you 
can't delete an extended slice by assignment, only by using del.

>>> s = range(10)
>>> del s[::2]
>>> s
[1, 3, 5, 7, 9]
>>> s = range(10)
>>> s[::2] = []

Traceback (most recent call last):
  File "<pyshell#19>", line 1, in -toplevel-
    s[::2] = []
ValueError: attempt to assign sequence of size 0 to extended slice of size 
5
>>>