[Tutor] s[len(s):len(s)] = [x] ??

[Dick Moores]

I'm very familiar with appending x to a list, s, using s.append(x), 
however, I've never understood what the docs mean by

s.append(x) same as s[len(s):len(s)] = [x]
(See <http://docs.python.org/lib/typesseq-mutable.html>)

Trying it,

 >>> s = [1,2,3]
 >>> x = 5
 >>> s[len(s):len(s)] = [x]
 >>> s[len(s):len(s)]
[]
 >>>

I'm not enlightened. Just what do the docs mean?

Thanks,

Dick Moores