Automaton Characteristics

Automaton instances are immutable

All Automaton instances are fully immutable to protect against common pitfalls, such as mutating an automaton to an invalid state after it's already been validated.

This means that if you wish to make a change to an automaton instance, you must retrieve its attributes as a dictionary (using the input_parameters property), make your desired change, then pass those parameters to the relevant constructor. For example:

from automata.fa.dfa import DFA

dfa1 = DFA(
    states={'q0', 'q1', 'q2'},
    input_symbols={'0', '1'},
    transitions={
        'q0': {'0': 'q0', '1': 'q1'},
        'q1': {'0': 'q0', '1': 'q2'},
        'q2': {'0': 'q2', '1': 'q1'}
    },
    initial_state='q0',
    final_states={'q1'}
)
# If you want to make a change, you must create a new instance; please note
# that dfa1.input_parameters is always a deep copy of the input parameters for
# dfa1 (in other words, mutating dfa1.input_parameters will not actually mutate
# dfa1)
params = dfa1.input_parameters
params['final_states'] = {'q2'}
dfa2 = DFA(**params)

Enabling mutable automata

Automaton immutability is enforced via a "freeze" step during object initialization that turns mutable parameters (such as sets or dicts) into their immutable counterparts (frozensets/frozendicts).

If your application requires maximum performance, you can disable this conversion via the allow_mutable_automata global configuration option. If enabled, the user must ensure that their automaton instances are never modified, otherwise correct behavior cannot be guaranteed.

import automata.base.config as global_config

global_config.allow_mutable_automata = True
# The rest of your code...

Automaton instances are validated by default

By default, all Automaton instances are checked for common inconsistencies when they are instantiated. If inconsistencies are found, the appropriate exception from automata.base.exceptions is raised.

Because this validation can be performance-intensive for large automaton instances with many states/transitions, you can disable the automatic validation using the global configuration feature (introduced in v7):

import automata.base.config as global_config

global_config.should_validate_automata = False

# The rest of your code...

If, at any point, you wish to opt into validation for a specific Automaton instance, you can call the validate method:

my_automaton.validate()