simple_dfa.py

class DFA:
    def __init__(self):
        self.states = ['q0', 'q1']
        self.alphabet = ['0', '1']
        self.transition_function = {
            ('q0', '0'): 'q1',
            ('q0', '1'): 'q0',
            ('q1', '0'): 'q0',
            ('q1', '1'): 'q1',
        }
        self.start_state = 'q0'
        self.accept_states = ['q0']

    def accepts(self, input_string):
        current_state = self.start_state
        for symbol in input_string:
            if symbol not in self.alphabet:
                return False  # Reject if an invalid symbol is found
            current_state = self.transition_function[(current_state, symbol)]
        return current_state in self.accept_states


# Example usage
dfa = DFA()
print(dfa.accepts("0101"))  # Should return True, even number of 0s
print(dfa.accepts("010101"))  # Should return False, odd number of 0s