[Python-Dev] partition() (was: Remove str.find in 3.0?)

Tue Aug 30 10:11:23 CEST 2005

Well, I want to come back on a point that wasn't discussed. I only found
one positive comment here :
http://mail.python.org/pipermail/python-dev/2005-August/055775.html
It's about that :
Raymond Hettinger wrote:
> * The function always succeeds unless the separator argument is not a
> string type or is an empty string. So, a typical call doesn't have to
> be wrapped in a try-suite for normal usage.

Well, I wonder if it's so good ! Almost all the use case I find would
require something like:
head, sep, tail = s.partition(t)
if sep:
 do something
else:
 do something else
Like, if you want to extract the drive letter from a windows path :
drive, sep, tail = path.partition(":")
if not sep:
 drive = get_current_drive() # Because it's a local path
Or, if I want to iterate over all the path parts in a UNIX path:
sep = '/'
while sep:
 head, sep, path = path.partition(sep)
IMO, that read strange ... partitionning until sep is None :S
Then, testing with "if" in Python is always a lot slower than having an
exception launched from C extension inside a try...except block.
So both construct would read like already a lot of Python code:
try:
 head,sep,tail = s.partition(t)
 do something
except SeparatorException:
 do something else
and:
sep='/'
try:
 while 1:
 head, drop, path = path.partition(sep)
except SeparatorException:
 The end
To me, the try..except block to test end or error conditions are just
part of Python design. So I don't understand why you don't want it !
For the separator, keeping it in the return values may be very useful,
mainly because I would really like to use this function replacing string
with a regexp (like a simplified version of the Qt method
QStringList::split) and, in that case, the separator would be the actual
matched separator string.
Pierre
-- 
Pierre Barbier de Reuille
INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP
Botanique et Bio-informatique de l'Architecture des Plantes
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