Raymond Hettinger wrote:
> [Marc-Andre Lemburg]
>
>>I may be missing something, but why invent yet another parsing
>>method - we already have the re module. I'd suggest to
>>use it :-)
>>
>>If re is not fast enough or you want more control over the
>>parsing process, you could also have a look at mxTextTools:
>>
>> http://www.egenix.com/files/python/mxTextTools.html
>
>
> Both are excellent tools. Neither is as lightweight, as trivial to
> learn, or as transparently obvious as the proposed s.partition(sep).
> The idea is to find a viable replacement for s.find().
Your partition idea could be had with an additional argument
to .split() (e.g. keepsep=1); no need to learn a new method.
Also, as I understand Terry's request, .find() should be removed
in favor of just leaving .index() (which is the identical method
without the funny -1 return code logic).
So your proposal really doesn't have all that much to do
with Terry's request, but is a new and separate proposal
(which does have some value in few cases, but not enough
to warrant a new method).
> Looking at sample code transformations shows that the high-power
> mxTextTools and re approaches do not simplify code that currently uses
> s.find(). In contrast, the proposed partition() method is a joy to use
> and has no surprises. The following code transformation shows
> unbeatable simplicity and clarity.
>
>
> --- From CGIHTTPServer.py ---------------
>
> def run_cgi(self):
> """Execute a CGI script."""
> dir, rest = self.cgi_info
> i = rest.rfind('?')
> if i >= 0:
> rest, query = rest[:i], rest[i+1:]
> else:
> query = ''
> i = rest.find('/')
> if i >= 0:
> script, rest = rest[:i], rest[i:]
> else:
> script, rest = rest, ''
> . . .
>
>
> def run_cgi(self):
> """Execute a CGI script."""
> dir, rest = self.cgi_info
> rest, _, query = rest.rpartition('?')
> script, _, rest = rest.partition('/')
Wouldn't this do the same ?! ...
rest, query = rest.rsplit('?', maxsplit=1)
script, rest = rest.split('/', maxsplit=1)
> . . .
>
>
> The new proposal does not help every use case though. In
> ConfigParser.py, the problem description reads, "a semi-colon is a
> comment delimiter only if it follows a spacing character". This cries
> out for a regular expression. In StringIO.py, since the task at hand IS
> calculating an index, an indexless higher level construct doesn't help.
> However, many of the other s.find() use cases in the library simplify as
> readily and directly as the above cgi server example.
>
>
>
> Raymond
>
>
> -------------------------------------------------------
>
> P.S. FWIW, if you want to experiment with it, here a concrete
> implementation of partition() expressed as a function:
>
> def partition(s, t):
> """ Returns a three element tuple, (head, sep, tail) where:
>
> head + sep + tail == s
> t not in head
> sep == '' or sep is t
> bool(sep) == (t in s) # sep indicates if the string was
> found
>
> >>> s = 'http://www.python.org'
> >>> partition(s, '://')
> ('http', '://', 'www.python.org')
> >>> partition(s, '?')
> ('http://www.python.org', '', '')
> >>> partition(s, 'http://')
> ('', 'http://', 'www.python.org')
> >>> partition(s, 'org')
> ('http://www.python.', 'org', '')
>
> """
> if not isinstance(t, basestring) or not t:
> raise ValueError('partititon argument must be a non-empty
> string')
> parts = s.split(t, 1)
> if len(parts) == 1:
> result = (s, '', '')
> else:
> result = (parts[0], t, parts[1])
> assert len(result) == 3
> assert ''.join(result) == s
> assert result[1] == '' or result[1] is t
> assert t not in result[0]
> return result
>
>
> import doctest
> print doctest.testmod()
--
Marc-Andre Lemburg
eGenix.com
Professional Python Services directly from the Source (#1, Aug 28 2005)
>>> Python/Zope Consulting and Support ... http://www.egenix.com/
>>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/
>>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/
________________________________________________________________________
::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,FreeBSD for free ! ::::
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
