Besides just abundant trial and error, there's a great Python module call greenery, that produces Finite State Machines from any Regular Expression: https://gi

Besides just abundant trial and error, there's a great Python module call greenery, that produces Finite State Machines from any Regular Expression: https://github.com/qntm/greenery https://github.com/qntm/greenery So, you can observe what kind of state machine is produced from any given Regular Expression. You can also use it to merge and such manipulate state machines, or simplify Regular Expressions. Quite helpful.