I am evaluating serverless v AWS SAM CLI.
I am trying to understand how can i facilitate a local dev workflow when developing using the following:-

• Lambda’s written in python
• Triggered by SNS notifications with an SES
  mail payload
• Reading S3 objects
• Reading and writing dynamodb
• Writing to SQS
• Writing to SNS topic

I can see from the doc that serverless has local options for:-

• S3
• DynamoDB
• SNS events inbound

Not obvious if there is a solution for:-

• API Gateway local supporting python lambdas
• Writing to SQS
• Writing to SNS

I can see from the SAM doc that its possible to test python Lambdas against local DynamoDB. Not clear what else is possible or if you have to point it to a an actual AWS instance for the rest (S3, SQS etc)

Any pointers?

I would look into leveraging something like https://github.com/localstack/localstack to achive SQS and SNS.

For APIGW endpoint this is built into sam-cli in your SAM template using the Events param on your function resource or using API resources. See API section in following link
https://docs.aws.amazon.com/lambda/latest/dg/serverless_app.html

Although it does not have complete functionality yet so it might not have everything you need like request body validation for example. I usually find I can do most of my app testing locally with this before deploying and doing more integration testing in real env.