One line finite-state machine implementation

olfsm.py

# State machine implementation:
olfsm = lambda Q, input, init: reduce(lambda o, i: o + (o[-1] if i not in Q[o[-1]] else Q[o[-1]][i]), input, init)

test-olfsm.py

from olfsm import olfsm

# Example transition matrix
Q = {
    '1': {'c': '4', 'b': '3'},
    '2': {'a': '1'},
    '3': {'a': '1'},
    '4': {'c': '3', 'b': '2'}
}

# Example inputs
I = list('aacabcaabacccabacabaccccaaabacbbcaac')

#example usage
print olfsm(Q,I,'1')

# output: 1114422113143313144214333111314222114