Python 转换：如何将 FSM 的所有可能转换映射到图形

Question

我无法在我的 Windows 10 系统上安装 pygraphviz，因此作为解决方法，我尝试将 FSM 的状态和转换存储在单独的图形中。例如：

from transitions import Machine
from graphviz import Digraph

class Matter(object):
    pass

# The states
states=['hungry', 'satisfied', 'full', 'sick']

# And some transitions between states. 
transitions = [
     { 'trigger': 'eat', 'source': 'hungry', 'dest': 'satisfied' },
     { 'trigger': 'eat', 'source': 'satisfied', 'dest': 'full' },
     { 'trigger': 'eat', 'source': 'full', 'dest': 'sick' },
     { 'trigger': 'rest', 'source': ['satisfied', 'full', 'sick'], 'dest': 
      'hungry' }]


# Initialize
machine = Matter()
fsm = Machine(machine, states=states, transitions=transitions, initial=states[0])
dot = Digraph(comment='FSM')

src = machine.state

for event in transitions:
    machine.trigger(event['trigger'])
    dst = machine.state
    dot.edge(src,dst,event['trigger'])
    src = dst

print (dot)

这里我的图表不包括所有可能的转换，只包括顺序转换。

输出：

digraph {
    hungry -> satisfied [label=eat]
    satisfied -> full [label=eat]
    full -> sick [label=eat]
    sick -> hungry [label=rest]
}

如您所见，图中不存在多个状态转换。有没有一种方法可以触发所有转换并将其存储在图形中，或者我是否必须编写自定义代码才能使所有这些都起作用。

Answer 1

transitions 组织事件转换。 Event 可能包含多个转换，同样组织在字典中。要实现您的愿望，首先遍历事件字典（键是触发器名称，值是 Event 本身）以获取事件。然后，遍历 Event.transitions（键是源状态，值是适用的 Transition 对象的列表）以获得转换列表。现在，迭代此列表以获取每个转换的源和目标。如果您愿意，可以使用触发器名称作为标签：

from transitions import Machine
from graphviz import Digraph


class Matter(object):
    pass


# The states
states = ['hungry', 'satisfied', 'full', 'sick']

# And some transitions between states.
transitions = [{'trigger': 'eat', 'source': 'hungry', 'dest': 'satisfied'},
               {'trigger': 'eat', 'source': 'satisfied', 'dest': 'full'},
               {'trigger': 'eat', 'source': 'full', 'dest': 'sick'},
               {'trigger': 'rest', 'source': ['satisfied', 'full', 'sick'],
                'dest': 'hungry'}]


# Initialize
machine = Matter()
fsm = Machine(machine, states=states, transitions=transitions, initial=states[0],
              auto_transitions=False)
dot = Digraph(comment='FSM')

for label, event in fsm.events.items():
    for event_transitions in event.transitions.values():
        for transition in event_transitions:
            dot.edge(transition.source, transition.dest, label)
print(dot)

输出：

// FSM
digraph {
    hungry -> satisfied [label=eat]
    satisfied -> full [label=eat]
    full -> sick [label=eat]
    satisfied -> hungry [label=rest]
    full -> hungry [label=rest]
    sick -> hungry [label=rest]
}

我还添加了 auto_transitions=False 到你的 Machine。这样 transitions 将不会生成自动转换 (to_<state_name>)，否则会使您的图形混乱。当然，您可以修改 auto_transitions=True 或尝试从图中过滤自动转换，如 transitions' diagrams extension.

中所做的那样

Python 转换：如何将 FSM 的所有可能转换映射到图形

Python Transitions: how to map all possible transitions of an FSM to a graph

python

graphviz

transitions

fsm

pygraphviz