Coding a simple state machine in python

[William Ray Wing]

On Feb 24, 2014, at 8:30 PM, Ronaldo <abhishek1899 at gmail.com> wrote:

> How do I write a state machine in python? I have identified the states and the conditions. Is it possible to do simple a if-then-else sort of an algorithm? Below is some pseudo code:
> 
> if state == "ABC":
>   do_something()
>   change state to DEF
> 
> if state == "DEF"
>   perform_the_next_function()
> ...
> 
> I have a class to which certain values are passed from a GUI and the functions above have to make use of those variables. How do I go about doing this? I have the following algorithm:
> 
> class TestClass():
>    def __init__(self, var1, var2): #var1 and var2 are received from a GUI
>       self.var1 = var1
> ...
>    if state == "ABC"
>       doSomething(var1, var2)
> ..
> 
> Could someone point me in the right direction? Thank you!
> 
> -- 
> https://mail.python.org/mailman/listinfo/python-list

And, to extend Tim's suggestion of a dictionary just a bit, note that since Python functions are happy to pass function names as arguments, you can use a dictionary to make a really nice compact dispatch table.  That is, function A does its thing, gets to a new state, and returns as one of its return arguments the key into the dictionary that points to the next function_name to be called based on that new state.

Stackoverflow has a couple of compact examples here:  

http://stackoverflow.com/questions/715457/how-do-you-implement-a-dispatch-table-in-your-language-of-choice

Bill