I use if__name__main__ often when working with AWS Lambda, but I also want to run it locally. Lambda wants to call a function with the params event and context. So I would do something like this:

def handler(event, context):
    things
    return {
        'statusCode': 200,
        'body': 'Hello from Lambda!'
    }

if __name__ == '__main__':
    event = {}
    context = {}
    response = handler(event, context)
    print(response)