Mastering Python Design Patterns by Kamon Ayeva
 and Sakis Kasampalis

Author:Kamon Ayeva
 and Sakis Kasampalis
Language: eng
Format: epub
Publisher: Packt Publishing Pvt Ltd
Published: 2024-05-24T00:00:00+00:00

Here’s what we get when executing the Python ch05/state.py command:

state of process1: created state of process2: created process1 entered waiting mode Transition of process2 from created to terminated failed state of process1: waiting state of process2: created process1 is running process2 entered waiting mode state of process1: running state of process2: waiting process2 is running state of process1: running state of process2: running process1 is blocked process2 is blocked state of process1: blocked state of process2: blocked Transition of process1 from blocked to terminated failed Transition of process2 from blocked to terminated failed state of process1: blocked state of process2: blocked

Indeed, the output shows that illegal transitions such as created → terminated and blocked → terminated fail gracefully. We don’t want the application to crash when an illegal transition is requested, and this is handled properly by the except block.

Notice how using a good module such as state_machine eliminates conditional logic. There’s no need to use long and error-prone if…else statements that check for each and every state transition and react to them.

To get a better feeling for the state pattern and state machines, I strongly recommend you implement your own example. This can be anything: a simple video game (you can use state machines to handle the states of the main hero and the enemies), an elevator, a parser, or any other system that can be modeled using state machines.

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