Shannon -jj Behrens wrote: > On 4/20/05, M.-A. Lemburg <[EMAIL PROTECTED]> wrote: > >>Fredrik Lundh wrote: >> >>>PS. a side effect of the for-in pattern is that I'm beginning to feel >>>that Python >>>might need a nice "switch" statement based on dictionary lookups, so I can >>>replace multiple callbacks with a single loop body, without writing too >>>many >>>if/elif clauses. >> >>PEP 275 anyone ? (http://www.python.org/peps/pep-0275.html) >> >>My use case for switch is that of a parser switching on tokens. >> >>mxTextTools applications would greatly benefit from being able >>to branch on tokens quickly. Currently, there's only callbacks, >>dict-to-method branching or long if-elif-elif-...-elif-else. > > I think "match" from Ocaml would be a much nicer addition to Python > than "switch" from C.
PEP 275 is about branching based on dictionary lookups which is somewhat different than pattern matching - for which we already have lots and lots of different tools. The motivation behind the switch statement idea is that of interpreting the multi-state outcome of some analysis that you perform on data. The main benefit is avoiding Python function calls which are very slow compared to branching to inlined Python code. Having a simple switch statement would enable writing very fast parsers in Python - you'd let one of the existing tokenizers such as mxTextTools, re or one of the xml libs create the token input data and then work on the result using a switch statement. Instead of having one function call per token, you'd only have a single dict lookup. BTW, has anyone in this thread actually read the PEP 275 ? -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Apr 25 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
