Jack Keegan, 04.09.2010 15:36:
Hi girls& guys,
Just joined the group. I'm new to Python but been picking it up pretty easy.
I love it!
Welcome to the group.
I'm hoping to use it to make a controlling application for an
experiment. Basically I want to use it to interface with some data
acquisition (DAQ) hardware to accept incoming signals and respond sending
signals to the outputs. I'm looking for an efficient State Machine algorithm
as I need the timing to be as good as possible.
As there is no switch statement in Python, I've been looking around for a
good implementation. Most of the algorithms I've come across seem to be
based on parsing applications. I'd like something more suited to my needs.
I'd like to avoid excessive use of 'if-elif-else' statements as each would
have to be checked to find the right conditions which would have an time
overhead involved. I have seen an implementation of the switch using
dictionaries but someone had commented that creating and throwing away
dictionaries also comes at a cost.
I was wondering if any of you could advise or point me in the right
direction.
Dictionaries are a common way to do it, and there are different recipes. A
second way is a class that dispatches to its methods. A third (IMHO rather
beautiful) way is coroutines:
http://gnosis.cx/publish/programming/charming_python_b5.html
http://www.dabeaz.com/coroutines/Coroutines.pdf
However, you'll have to do some benchmarking if you care about performance.
Dictionaries are fast and likely the fastest way to do it, but coroutines
are a lot more versatile. Stackless Python might also be worth a look in
this context, it's fast *and* versatile.
You should also be aware that there are various event driven frameworks
(like Twisted, eventlet and others) that make asynchronous event handling
fast and easy, and that use much higher-level abstractions than pure state
machines.
Stefan
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