Part of the text of the online documentation for the string.split() method:

<snip>
If sep is not specified or is None, a different splitting algorithm is
applied. First, whitespace characters (spaces, tabs, newlines, returns,
and formfeeds) are stripped from both ends. Then, words are separated by
arbitrary length strings of whitespace characters. Consecutive
whitespace delimiters are treated as a single delimiter ("'1 2
3'.split()" returns "['1', '2', '3']"). Splitting an empty string or a
string consisting of just whitespace returns an empty list.
</snip>

As you may have noticed, there should be multiple spaces in ("'1 2
3'.split()". If you look at the HTML source you will see that they are
there. However, because browsers rendering HTML by default replace
multiple space with a single space, they are not visible in the
documentation. This should be addressed by either using <PRE></PRE>
around the text to preserve formatting or by replacing all instances of
multiple spaces with instances of "&nbsp;". I suspect this problem may
be elsewhere in the documentation as well.

This is fixed in the new docs, see
<http://docs.python.org/library/stdtypes#str.split>.