This Lambda will retrieve parameters from an API gateway request and then initiate a Step Functions workflow

stepfunctionsinitiatefromlambda.py

import json, boto3, os

def lambda_handler(event, context):
    
    if event['queryStringParameters']['program'] is None:
        return {"isBase64Encoded":False,"statusCode":400,"body":json.dumps({"error":"Missing program name."})}
    if event['queryStringParameters']['operation'] is None:
        return {"isBase64Encoded":False,"statusCode":400,"body":json.dumps({"error":"Missing operation name."})}
    programName = str(event['queryStringParameters']['program'])
    operationName = str(event['queryStringParameters']['operation'])
    
    stateInput = f'''
    {{
      "program": "{programName}",
      "operation": "{operationName}"
    }}
    '''

    my_state_machine_arn = 'arn:aws:states:us-east-1:00000000000:stateMachine:customname'
    client = boto3.client('stepfunctions')
    response = client.start_execution(
        stateMachineArn=my_state_machine_arn,
            input=stateInput
        )
    
    responseData = {
        'Program Status': 'Success'
    }
    
    return {
        'statusCode': 200,
        'body': json.dumps(responseData)
    }