decorstate

decorstate

Build dumb little "state machines" with Python decorators.

Installation

To install decorstate from pip:

    $ pip install decorstate

To install decorstate from source:

    $ git clone [e-mail]:ahawker/decorstate.git
    $ cd decorstate
    $ python setup.py install

Usage

How do I use this pile?

import decorstate

class Switch(object):
    state = 'off'

    @decorstate.transition('off', 'on')
    def on(self, *args, **kwargs):
        print 'You turned me on!'

    @decorstate.transition('on', 'off')
    def off(self, *args, **kwargs):
        print 'You turned me off!'

>>> switch = Switch()
>>> switch.state
'off'
>>> switch.on()
You turned me on!
'on'
>>> switch.off()
You turned me off!
'off'

A switch? Really? How lame.

import decorstate

class BrokenSwitch(object):
    state = 'off'

    @decorstate.transition('off', 'on')
    def on(self, *args, **kwargs):
        print 'You turned me on!'

    @decorstate.transition('on', 'off')
    def off(self, *args, **kwargs):
        print 'You turned me off? Nah!'

    @off.guard
    def off(self, *args, **kwargs):
        print 'Ha! I laugh at your feeble attempt!'

>>> broken_switch = BrokenSwitch()
>>> broken_switch.state
'off'
>>> broken_switch.on()
You turned me on!
'on'
>>> broken_switch.off()
Ha! I laugh at your feeble attempt!
'on'
>>> broken_switch.state
'on'
>>> broken_switch.off()
Ha! I laugh at your feeble attempt!
'on'
>>> broken_switch.state
'on'

A broken switch? Yawn.

import decorstate

class InstantOffSwitch(object):
    state = 'off'

    @decorstate.transition('off', 'off')
    def on(self, *args, **kwargs):
        print 'You turned me on!'

    @decorstate.transition('on', 'off')
    def off(self, *args, **kwargs):
        print 'You turned me off!'

    @on.after
    def on(self, *args, **kwargs):
        print 'Ha! No light for you!'

>>> instant_off_switch = InstantOffSwitch()
>>> instant_off_switch.state
'off'
>>> instant_off_switch.on()
You turned me on!
Ha! No light for you!
'off'
>>> instant_off_switch.state
'off'

Well, that's kinda mean.

import decorstate
import random

class IoTSwitch(object):
    state = 'off'

    @decorstate.transition('off', 'off')
    def on(self, *args, **kwargs):
        print 'You turned me on? Maybe...'

    @decorstate.transition('on', 'off')
    def off(self, *args, **kwargs):
        print 'You turned me off? Maybe...'

    @on.guard
    def on(self, *args, **kwargs):
        return self.coin_flip()

    @off.guard
    def off(self, *args, **kwargs):
        return not self.coin_flip()

    @staticmethod
    def coin_flip():
        return random.randint(1, 2) == 1

>>> iot_switch = IoTSwitch()
>>> iot_switch.state
'off'
>>> iot_switch.on()
'off'
>>> iot_switch.on()
'off'
>>> iot_switch.on()
'off'
>>> iot_switch.on()
You turned me on? Maybe...
'on'
>>> iot_switch.off()
'on'
>>> iot_switch.off()
'on'
>>> iot_switch.off()
'on'
>>> iot_switch.off()
'on'
>>> iot_switch.off()
You turned me off? Maybe...
'off'

Hey now, why you hating? Internet powered light switches are next level shit. My living room has its own twitter feed.

Why?

I was interesting in doing something a bit more complex using the Python descriptor protocol.

TODO?

Random thoughts and musing about potential changes/features.

• Consider adding the @machine decorator back as currently, you cannot use the "state", "transition" and "transition_event" attributes until the first transition has been performed since they are lazy created.
• Add event handler that fires only when "entering" a state and not when you perform multiple transitions but stay in the same state.

License

Apache 2.0