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https://github.com/marcinn/dsm
Damn simple finite state machine for Python
https://github.com/marcinn/dsm
declarative django finite-state-machine fsm imperative library python python2 python3 state-machine
Last synced: 2 months ago
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Damn simple finite state machine for Python
- Host: GitHub
- URL: https://github.com/marcinn/dsm
- Owner: marcinn
- License: bsd-4-clause
- Created: 2015-07-03T14:43:09.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2020-03-17T22:54:47.000Z (almost 5 years ago)
- Last Synced: 2024-11-24T14:41:08.041Z (3 months ago)
- Topics: declarative, django, finite-state-machine, fsm, imperative, library, python, python2, python3, state-machine
- Language: Python
- Homepage:
- Size: 15.6 KB
- Stars: 5
- Watchers: 1
- Forks: 1
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# dsm
Damn simple finite state machine
[](https://travis-ci.org/marcinn/dsm)
## About
DSM is a observable simple finite state machine implementation for Python.
Transitions may be programmed declaratively or imperatively.
Inputs and state changes are emitting observable events.
## Requirements
- Python 2.7, 3.5, 3.6
- ``observable``
- ``six`` for compatibility between Python 2 and Python 3
## Installation
pip install dsm
## Usage
### Django integration
It is possible to integrate `dsm` with Django models by
declaring a `StateMachineField`.
```python
from django.db import models
from dsm.fields import StateMachineField
class Order(models.Model):
status = StateMachineField(
transitions=(
('new', ['confirmed'], 'processing'),
('processing', ['cancel'], 'cancelled'),
('processing', ['send'], 'sending'),
('sending', ['deliver'], 'finished'),
),
max_length=16,
choices=(
('new', _('New')),
('processing', _('Processing')),
('sending', _('Sending')),
('finished', _('Finished')),
('canceled', _('Cancelled')),
),
db_index=True,
default='new'
)
```
Now you can create an `Order` and check it's status:
```python
>>> order = Order.objects.create()
>>> order.status
new
>>> type(order.status)
dsm.fields.MachineState
```
The string representation of `status` field is same as state name
provided in transitions declaration, but internally there is always
`dsm.fields.MachineState` instance.
### Declarative
FSM declaration:
```python
import string
import dsm
class SumatorMachine(dsm.StateMachine):
class Meta:
initial = 'init'
transitions = (
('init', list(string.digits), 'digit_enter'),
('digit_enter', list(string.digits), 'digit_enter'),
('digit_enter', '=', 'summarize'),
)
```
### Usage:
Initialization:
```python
fsm = SumatorMachine()
```
Processing one value:
```python
fsm.process(value)
```
Processing multiple values:
```python
fsm.process_many(iterable)
```
Gathering the current state:
```python
>>> fsm.state
'summarize'
```
Resetting to the intial state:
```python
fsm.reset()
```
Listening on events:
```python
fsm.when('state', func)
```
Events example:
```python
>>> the_sum = 0
>>> def add_digit(x): global the_sum; the_sum += int(x)
>>> def reset(x): global the_sum; the_sum = 0
>>> fsm = SumatorMachine()
>>> fsm.when('digit_enter', add_digit)
>>> fsm.when('init', reset)
>>> fsm.process_many('666=')
'summarize'
>>> the_sum
18
```
Events example (class based):
```python
>>> class Sumator(object):
... def __init__(self):
... self.total = 0
... self.fsm = SumatorMachine()
... self.fsm.when('digit_enter', self.add)
... self.fsm.when('init', self.reset)
...
... def add(self, x):
... self.total += int(x)
...
... def reset(self, x):
... self.total = 0
...
... def summarize(self, values):
... self.fsm.reset()
... self.fsm.process_many(values+'=')
... return self.total
>>> s = Sumator()
>>> s.summarize('666')
18
```
### Imperative
```python
import string
import dsm
fsm = dsm.StateMachine(
initial='init',
transitions=dsm.Transitions((
('init', list(string.digits), 'digit_enter'),
('digit_enter', list(string.digits), 'digit_enter'),
('digit_enter', '=', 'summarize'),
))
)
```
## License
BSD