State feature: Timeout

Adds the ability to timeout an entered state. See: states.py

Keywords

• timeout (int, optional) – if passed, an entered state will timeout after timeout seconds
• on_timeout (string/callable, optional) – will be called when timeout time has been reached

Exceptions:

• will raise an AttributeError when timeout is set but on_timeout is not

Example Usage

from transitions import Machine
from transitions.extensions.states import add_state_features, Timeout

import time


@add_state_features(Timeout)
class CustomMachine(Machine):
    pass


class Model(object):

    def timeout(self):
        print("Timeout!")
        self.to_A()

model = Model()

states = ['A',
          {'name': 'B', 'timeout': 0.3, 'on_timeout': 'timeout'},
          {'name': 'C', 'timeout': 0.9, 'on_timeout': model.timeout}]

m = CustomMachine(model, states=states, initial='A')
model.to_B()
time.sleep(1)  # >>> "Timeout!"
print model.state  # >>>  'A'

Remark

This implementation is not thread-safe! The user may either lock the model or use LockedMachine.

[Synss]

Hi, great to see this coming. Just two small things: could you put a comment to #198: I was following #198 and overlooked this thread until yesterday. I would also check the presence of on_timeout with EAFP

index 40e9ce7..1d8a01f 100644
--- a/transitions/extensions/states.py
+++ b/transitions/extensions/states.py
@@ -36,8 +36,9 @@ class Timeout(object):
     def __init__(self, *args, **kwargs):
         self.timeout = kwargs.pop('timeout', 0)
         if self.timeout > 0:
-            self.on_timeout = kwargs.pop('on_timeout', None)
-            if self.on_timeout is None:
+            try:
+                self.on_timeout = kwargs["on_timeout"]
+            except KeyError as exc:
                 raise AttributeError("Timeout state requires 'on_timeout' when timeout is set.")
         self.runner = {}
         super(Timeout, self).__init__(*args, **kwargs)

This way, you avoid the if in the normal case.

[aleneum]

Have you started working on this?

has been implemented and tested. Hope this enables your workflow.