wave hullo folks have a general question about flows vs task

Question

wave hullo folks have a general question about flows vs tasks vs just regular functions in prefect 2 0 are there any high level guidelines on where we may want to use each i ll try to describe a scenario in the thread

Jai P · Answer

let s say we have some plain python code ```def a def b def c b def d b c ``` there are a number of scenarios we could structure this where some things are ` flow`s some things are ` task`s or there s only one flow at the top and everything else is tasks or everything is marked as a ` flow` etc etc

Jai P · Answer

i guess i m not looking for the optimal solution for the example above but more hey i have a function when might i want to mark it as a task or a flow and what are the tradeoffs of doing so

Zanie · Answer

A major difference is that flows block execution while tasks are run in the background

Zanie · Answer

If you call a flow it will not return until its final state is reached If you call a task it returns a future immediately and the return value can be retrieved later

Jai P · Answer

i can trigger multiple flows in parallel though right but maybe that adds some clarity about how much you want to deeply nest things as flows

Anna Geller · Answer

We have this Discourse page that may help I added Michael s info there Regarding running flows in parallel you could do ``` flow async def main flow parallel subflows = subflow 1 subflow 2 subflow 3 subflow 4 await asyncio gather parallel subflows ``` more on that

Zanie · Answer

We re also likely to add an interface for running flows in parallel without using async in the future

Jai P · Answer

amazing and again tasks can t call other tasks right so if i have a situation where i d want to say programmatically call some set of tasks conditionally it may be better to have those tasks called via some function rather than a subflow especially if i don t want the blocking behavior

Jai P · Answer

so like ``` task def a task def b something def c a result = a b result = b a result flow def d c ``` where if possible avoid making `c` a subflow unless its absolutely necessary maybe using a different taskrunner or storage or something

Zanie · Answer

Yep that makes sense

Zanie · Answer

The tasks would still run concurrently but only within the subflow They d all finish before the subflow returns

Jai P · Answer

gotcha gotcha ok thanks