Hi y’all. I’m getting started with Prefect this week and very excited! Question about script logic: does the

with Flow(...):

context manager basically replace using a

main()

function? i.e., instead of something like this:

from prefect import task, Flow

@task
def say_hello():
    print("Hello, world!")

@task
def say_goodbye():
    print("Goodbye, world!")    


with Flow("My First Flow") as flow:
    say_hello()
    say_goodbye()

Would

main()

be used with the context manager (and is it weird/redundant to do so)? i.e., would you decorate each function with

@task

, order them in

main()

(but not decorate

main()

) and then call

main()

from the context manager like so:

from prefect import task, Flow


@task
def say_hello():
    print("Hello, world!")


@task
def say_goodbye():
    print("Goodbye, world!")


def main():
    say_hello()
    say_goodbye()


if __name__ == "__main__":
    with Flow("My First Flow") as flow:
        main()

Thanks for any advice/insights on best practices around this!

I think it's unnecessary to use if name == "_main_" in general with prefect flows. The context manager is kind of like a main function. It's the highest level where your functions(tasks) are called. But I sometimes do use a main() function to group tasks together. For example, if you have 100 tasks, and you had 10 flows that are exactly the same except for their parameters, you could use a the same main function under each Flow, instead of calling each task under each Flow.

Welcome @kiran! I'm sure there are other approaches within the community, but I'm gonna talk about what I usually do, and why I do those things. 1- Wrap the context manager with a

build_flow()

function. 2- Use

main()

to configure my

build_flow()

call, and also customize what to do with the built flow.

def build_flow(is_polite):
    with Flow('abc') as f:
        say_hello()
        if is_polite:
            say_goodbye()
    return flow
    
def main():
    # Here I can customize the flow I build without modifying the context manager
    flow = build_flow(True)

    # What I wanna do with the flow resides in main separated from what the flow consists of.
    # flow.run()
    flow.visualize()

Usually I implement a simple CLI inside my

main()

function, so I can pick what I wanna do and build without touching anything in the code.

I concur with @emre we create it own command line tool that standardize all the customization we need. Good to have the drain of the flow in one function as well

Thanks all for your input! Good things for me to think about. @emre are you not using Cloud to run your flows?

Not yet, but if i did, I would add registration as a cli option, then cloud would handle prod runs, and flow.run would handle development

Ah great. Thanks!