decorstate 0.0.1

Simple "state machines" with Python decorators

# decorstate

[](https://travis-ci.org/ahawker/decorstate)

Build dumb little "state machines" with Python decorators.

### Installation

To install decorstate from [pip](https://pypi.python.org/pypi/pip):
```bash
$ pip install decorstate
```

To install decorstate from source:
```bash
$ git clone [e-mail]:ahawker/decorstate.git
$ cd decorstate
$ python setup.py install
```

### Usage

How do I use this pile?

```python
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.


```python
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.


```python
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.


```python
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](https://docs.python.org/2/howto/descriptor.html).

### 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](LICENSE)