Hey, I'm new to prefect and have a question regarding sharing objects between different flows. I have two different flows,

flow_1

initializes the object and

flow_2

uses that object, but I'm not able to achieve this. This is the example code not exact but similar to what I'm trying to achieve. adding code to thread

Hey @Chhaya Vankhede, I think there are a couple of things off here. • The

StartFlowRun

is not actually called. It is a task so it should be used inside the Flow block like:

with Flow("parent-flow") as flow:
    flow_a = StartFlowRun(flow_name="flow_a", project_name="my project")
    b = flow_b(upstream_tasks=[flow_a])

•

flow_a

initializes the

a

and

b

but the they won’t be seen by

flow_b

. This is because tasks are only executed when Flows run, so that

initialise

only happens in

flow_a

. The idea was right there, but the thing is we can’t pass the data between Flow runs. There are a couple of ways to do this, but the Flows are executed as different processes so they don’t share variables. If your Flow requires then to share variables in memory, you should probably just stick to one flow.

from prefect import task, Flow
import prefect
from prefect.tasks.prefect import StartFlowRun

a = None
b = None

@task
def initialise():
    global a, b
    a = "hello "
    b = "world!"
    logger = prefect.context.get('logger')

    <http://logger.info|logger.info>("I actually requested this time...")

with Flow("flow_a") as f:
    initialise()

f.register(project_name="my project")
flow_a = StartFlowRun(flow_name="flow_a", project_name="my project")

@task
def add_str():
    global a, b
    logger = prefect.context.get('logger')
    <http://logger.info|logger.info>(a)
    <http://logger.info|logger.info>(b)
    c = a+b
 
    <http://logger.info|logger.info>(c)

with Flow("flow_b") as f:
    add_str()

f.register(project_name="my project")

flow_b = StartFlowRun(flow_name="flow_b", project_name="my project")

with Flow("parent-flow") as flow:
    b = flow_b(upstream_tasks=[flow_a])

flow.run()

Here

a

and

b

are global object which is used in

flow_a

and

flow_b

.

flow_a

and

flow_b

must be different. Any idea what's wrong here?

Thanks!