State Machines in Python

Sat Sep 4 09:49:53 EDT 2010

On Sat, 4 Sep 2010 14:36:38 +0100
Jack Keegan <whatsjacksemail at gmail.com> wrote:
> Just joined the group. I'm new to Python but been picking it up pretty easy.

Welcome aboard.
> 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

There's no switch statement because there's no real need for one.
Check out the following sample code and see if it gives you some ideas.
#! /usr/bin/env python
# -*- coding: utf-8 -*-
# Sample state machine
import sys
data = dict(counter = 0, flag = False)
def state1(d):
 d['counter'] += 1
 print "In state 1, counter = %(counter)d" % d
 if d['flag']: sys.exit(0)
 return state2
def state2(d):
 d['counter'] += 1
 print "In state 2, counter = %(counter)d" % d
 return state3
def state3(d):
 d['counter'] += 1
 d['flag'] = True
 print "In state 3, counter = %(counter)d" % d
 return state1
state = state1
while True:
 state = state(data)
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