python - Best way to pass around a boto3 client?

Question

I am often writing scripts with boto3 and usually when writing functions I end up passing the boto3 client for the service(s) I need around my functions. So, for example

def main():
    ec2 = create_client
    long_function_with_lots_of_steps(ec2, ....)

def long_function_with_lots_of_steps(client):
    ....

This is not too bad, but it often feels repetitive and sometimes I will need to create a new client for a different service in the other function, for which I would like to use the original aws_session object.

Is there a way to do this more elegantly? I thought to make a class holding a boto3.session.Session() object but then you end up just passing that around.

How do you usually structure boto3 scripts?

question from:https://stackoverflow.com/questions/65933583/best-way-to-pass-around-a-boto3-client

Answer 1

I think you might have had some C or C++ programming experience. You are definitely getting language constructs confused. In Python function call arguments are passed by reference. So passing a reference is quick. You aren't passing the whole object.

This is in fact one of the better ways to pass in session info. Why is it better you may ask? Because of testing. You will need to test the thing and you don't always want to test the connections to 3rd party services. So you can do that with Mocks.

Try making a test where you are mocking out any one of those function arguments. Go ahead... I'll wait.

Easier... right?