pytransitions库get_triggers()返回结果不符合预期问题咨询

Let's figure out why you're not getting the expected output from get_triggers() and fix it up. First, let's start with a working example that matches your transition setup—this will help you compare against your code.

Working Example Code #

from transitions import Machine

# Your transition definition (unchanged)
transitions = [
    {'trigger': 'melt', 'source': 'solid', 'dest': 'liquid'},
    {'trigger': 'evaporate', 'source': 'liquid', 'dest': 'gas'},
    {'trigger': 'sublimate', 'source': 'solid', 'dest': 'gas'},
    {'trigger': 'ionize', 'source': 'gas', 'dest': 'plasma'}
]

# A simple model class to attach the state machine to
class Matter:
    pass

# Initialize the state machine with your transitions and an initial state
matter = Matter()
machine = Machine(model=matter, transitions=transitions, initial='solid')

# Get triggers for specific states
print(machine.get_triggers('solid'))  # Output: ['melt', 'sublimate']
print(matter.get_triggers('liquid'))  # You can also call it directly on the model instance

Common Issues That Cause Unexpected get_triggers() Output #

Here are the most likely reasons your call isn't working as expected:

• You didn't specify an initial state or check the current state
  If you omit the initial parameter when creating the Machine, your model won't have a default state. Calling get_triggers() without a state argument will return triggers for the current state (which might be None, resulting in an empty list). Always verify your model's current state with print(matter.state) first.

• You're calling get_triggers() without a state parameter
  When you call get_triggers() without passing a state name, it returns triggers for the model's current state, not all states or a specific one you had in mind. For example, if your model is in the gas state, get_triggers() will only return ['ionize'].

• State name mismatch (case-sensitive!)
  pytransitions treats state names as case-sensitive. If you call get_triggers('Solid') instead of get_triggers('solid'), you'll get an empty list because the state doesn't exist. Double-check that the state name you pass exactly matches what's in your transition definitions.

• Your model isn't properly attached to the state machine
  If you forgot to pass model=matter when initializing Machine, or if you're using a model that wasn't bound to the state machine, calls to get_triggers() won't have access to your transition data. Make sure the model instance is linked during Machine setup.

Quick Debugging Steps #

1. Run print(matter.state) to confirm your model's current state.
2. Verify that the state name you pass to get_triggers() is spelled exactly (including case) as in your transitions.
3. Ensure your Machine initialization includes both the model and transitions parameters, plus an initial state if you need a starting point.

内容的提问来源于stack exchange，提问作者Ramaq