diff options
| -rwxr-xr-x | lib/automata.py | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/lib/automata.py b/lib/automata.py index 8e889aa..db7caf0 100755 --- a/lib/automata.py +++ b/lib/automata.py @@ -142,7 +142,10 @@ class State: :param transition_name: transition name :returns: `Transition` object """ - return self.outgoing_transitions[transition_name] + try: + return self.outgoing_transitions[transition_name] + except KeyError: + raise ValueError('State {} has no outgoing transition called {}'.format(self.name, transition_name)) from None def has_interrupt_transitions(self) -> bool: """Return whether this state has any outgoing interrupt transitions.""" |