On 8/31/05, Raymond Hettinger <[EMAIL PROTECTED]> wrote:
> [Hye-Shik Chang]
> > What would be a result for rpartition(s, '?') ?
> > ('', '', 'http://www.python.org')
> > or
> > ('http://www.python.org', '', '')
>
> The former. The invariants for rpartition() are a mirror image of those
> for partition().
Just to put my spoke in the wheel, I find the difference in the
ordering of return values for partition() and rpartition() confusing:
head, sep, remainder = partition(s)
remainder, sep, head = rpartition(s)
My first expectation for rpartition() was that it would return exactly
the same values as partition(), but just work from the end of the
string.
IOW, I expected "www.python.org".partition("python") to return exactly
the same as "www.python.org".rpartition("python")
To try out partition(), I wrote a quick version of split() using
partition, and using partition() was obvious and easy:
def mysplit(s, sep):
l = []
while s:
part, _, s = s.partition(sep)
l.append(part)
return l
I tripped up when trying to make an rsplit() (I'm using Python 2.3),
because the return values were in "reverse order"; I had expected the
only change to be using rpartition() instead of partition().
For a second example: one of the "fixed stdlib" examples that Raymond
posted actually uses rpartition and partition in two consecutive lines
-- I found this example not immediately obvious for the above reason:
def run_cgi(self):
"""Execute a CGI script."""
dir, rest = self.cgi_info
rest, _, query = rest.rpartition('?')
script, _, rest = rest.partition('/')
scriptname = dir + '/' + script
scriptfile = self.translate_path(scriptname)
if not os.path.exists(scriptfile):
Anyway, I'm definitely +1 on partition(), but -1 on rpartition()
returning in "reverse order".
Andrew
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