baseimage-tutorial-framework/lib/tfw/yaml_fsm.py

from subprocess import Popen
from functools import partial

import yaml
from transitions import State

from tfw import FSMBase


class YamlFSM(FSMBase):
    def __init__(self, config_file):
        self.config = self.parse_config(config_file)
        self.patch_config_callbacks()
        self.setup_states()
        super(YamlFSM, self).__init__()  # FSMBase.__init__() requires states
        self.setup_transitions()

    @staticmethod
    def parse_config(config_file):
        with open(config_file, 'r') as ifile:
            return yaml.load(ifile)

    def setup_states(self):
        self.states = [State(**state) for state in self.config['states']]

    def setup_transitions(self):
        for transition in self.config['transitions']:
            self.machine.add_transition(**transition)

    def patch_config_callbacks(self):
        topatch = {'on_enter', 'on_exit', 'prepare', 'before', 'after'}

        for array in {'states', 'transitions'}:
            for json_obj in self.config[array]:
                for attribute, value in json_obj.items():
                    if attribute in topatch:
                        json_obj[attribute] = partial(self.run, value)

    @staticmethod
    def run(command, event):
        Popen(command, shell=True)