Estado

Estado is a language for describing state machines.

Example interaction

Supposing a state machine consisting of two pass states, initialized as follows:

from estado.pass_state import Pass
machine = Pass(name="FirstPass") + Pass(name="SecondPass")

Note that this is equivalent to the following

from estado.input import Input
from estado.machine import Machine
from estado.pass_state import Pass

machine = Machine()
machine.register(Pass(name="FirstPass"))
machine.register(Pass(name="SecondPass"))

We can compile it to valid Amazon States Language with

machine.compile()

which returns

{
  "StartAt": "FirstPass",
  "States": {
    "FirstPass": {
      "Type": "Pass",
      "Next": "SecondPass",
      "End": false
    },
    "SecondPass": {
      "Type": "Pass",
      "End": true
    }
  }
}

We can interpret the machine with an initial input:

x = Input(x=5)
machine.interpret(input=x)

which returns the Estado representation <Input:input:5>.

Task states

There is support for interpreting task states. We can use the estado.resource_registry.Registry class to register function resources.

Given a registry initialized with a function:

from estado.resource_registry import Registry

registry = Registry()
add_two = lambda x: x + 2
registry.register_function(add_two, "add_two")

We can interpret a simple machine as follows:

from estado.input import Input
from estado.task_state import Task

first_state = Pass(
        name="state_one"
)
second_state = Task(
        name="AddTwo",
        resource="add_two",
        registry=registry
)

machine = first_state + second_state
machine.interpret(input=Input(x=5))

which returns <Result:result:7>, with compilation via the compile method outputting

{
  "StartAt": "state_one",
  "States": {
    "state_one": {
      "Type": "Pass",
      "Next": "add_two",
      "End": false
    },
    "AddTwo": {
      "Type": "Task",
      "End": true,
      "Resource": "registry:add_two"
    }
  }
}

Tests

To run the tests, ensure you have pytest on your path. Then do pytest from the project root.