/stairstep

A Pythonic API for Amazon's States Language for defining AWS Step Functions

Primary LanguagePythonMIT LicenseMIT

stairstep

StairStep is a Pythonic API for designing AWS Step Functions using Amazon's State Language

Instead of hand crafting JSON, StairStep allows you define step functions using Python code which allows you to easily import information from outside sources and dynamically create step functions on the fly.

Development Progress / Coverage

Lanuage Feature Type Progress
State Pass ✅
State Task ✅
State Succeed ✅
State Fail ✅
State Choice ✅
Field Common Validations ✅
State Wait ✅
State Parallel Next 🛣

Examples

Hello World

Using the example from the Amazon's State Language page

{
    "Comment": "A simple minimal example of the States language",
    "StartAt": "Hello World",
    "States": {
    "Hello World": { 
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:123456789012:function:HelloWorld",
      "End": true
    }
  }
}

We can easily craft that in StairStep as follows

# Create a parent StairStep object
ss = StairStep(comment="A simple minimal example of the States language", startAt="Hello World")

# Create the HelloWorld step
hello = StateTask(name="Hello World", resource="arn:aws:lambda:us-east-1:123456789012:function:HelloWorld", end=True)

# Add the step into the StairStep object
ss.addState(hello)

# Create the Amazon State Language Export
ss.json()

{  
   "Comment":"A simple minimal example of the States language",
   "StartAt":"Hello World",
   "States":{  
      "Hello World":{  
         "Type":"Task",
         "Resource":"arn:aws:lambda:us-east-1:123456789012:function:HelloWorld",
         "End":true
      }
   }
}

hello_world

Complex Choice State

ss = StairStep(
    comment = "Example Choice State",
    startAt = "ChoiceStateX"
)
# Create a ChoiceRule, which is composed of choice expression(s)
# This checks to see if the variable $.type is not "Private"
typeNotPrivate = ChoiceRule(operator="Not", snext="Public", conditions=
    ChoiceExpression(operator="StringEquals", variable="$.type", value="Private")
)

# This checks to see if the value of $.value is >=20 or <30
valueInTwenties = ChoiceRule(operator="And", snext="ValueInTwenties", conditions=
    [
        ChoiceExpression(operator="NumericGreaterThanEquals", variable="$.value", value=20),
        ChoiceExpression(operator="NumericLessThan", variable="$.value", value=30)
    ]
)
state = StateChoice(name="ChoiceStateX", choices=[typeNotPrivate,valueInTwenties],default="DefaultState")

default = StatePass(name="DefaultState", end=True)
in_twenties = StatePass(name="ValueInTwenties", end=True)
public = StatePass(name="Public", end=True)

ss.addState(state)
ss.addState(in_twenties)
ss.addState(public)
ss.addState(default)
ss.json()

{
	"Comment": "Example Choice State",
	"StartAt": "ChoiceStateX",
	"States": {
		"ChoiceStateX": {
			"Type": "Choice",
			"Default": "DefaultState",
			"Choices": [{
				"Next": "Public",
				"Not": {
					"Variable": "$.type",
					"StringEquals": "Private"
				}
			}, {
				"Next": "ValueInTwenties",
				"And": [{
					"Variable": "$.value",
					"NumericGreaterThanEquals": 20
				}, {
					"Variable": "$.value",
					"NumericLessThan": 30
				}]
			}]
		},
		"ValueInTwenties": {
			"Type": "Pass",
			"End": true
		},
		"Public": {
			"Type": "Pass",
			"End": true
		},
		"DefaultState": {
			"Type": "Pass",
			"End": true
		}
	}
}

choice_state