new string method in 2.5 (partition)

[John Salerno]

Forgive my excitement, especially if you are already aware of this, but 
this seems like the kind of feature that is easily overlooked (yet could 
be very useful):


Both 8-bit and Unicode strings have new partition(sep) and 
rpartition(sep) methods that simplify a common use case.
The find(S) method is often used to get an index which is then used to 
slice the string and obtain the pieces that are before and after the 
separator. partition(sep) condenses this pattern into a single method 
call that returns a 3-tuple containing the substring before the 
separator, the separator itself, and the substring after the separator. 
If the separator isn't found, the first element of the tuple is the 
entire string and the other two elements are empty. rpartition(sep) also 
returns a 3-tuple but starts searching from the end of the string; the 
"r" stands for 'reverse'.

Some examples:


 >>> ('http://www.python.org').partition('://')
('http', '://', 'www.python.org')
 >>> ('file:/usr/share/doc/index.html').partition('://')
('file:/usr/share/doc/index.html', '', '')
 >>> (u'Subject: a quick question').partition(':')
(u'Subject', u':', u' a quick question')
 >>> 'www.python.org'.rpartition('.')
('www.python', '.', 'org')
 >>> 'www.python.org'.rpartition(':')
('', '', 'www.python.org')

(Implemented by Fredrik Lundh following a suggestion by Raymond Hettinger.)