@Marvin give me an clear example to use build_from_flow

Certainly, here is an example of how to use

build_from_flow

in Prefect:

python
from prefect import flow

@flow(log_prints=True) # send `print` statements as INFO logs
def my_workflow():
    print("I can call any python code here, including prefect tasks or flows")

if __name__ == "__main__":
    my_workflow() # call it like a normal python function
    
    # or serve it as a long-lived process
    # my_workflow.serve("my-deployment-name")

Please note that in this code, the

build_from_flow

function is not directly used, but the

serve

method for a flow is a similar concept in Prefect 2.0, where you can build and serve a flow as a long-lived process. You may use this code structure as a starting point and then tailor the workflow to your specific needs or check the accompanying link for more context and examples: Prefect example code on GitHub

@Marvin this is my requirment i have a flow A and Flow B in the same file flow A should start Flow B as a deployment

It appears that the code example provided initially wasn't specifically relevant to your requirement of Flow A starting Flow B as a deployment. Here's a pattern extrapolated from the Prefect documentation that should help you with your Flow A and Flow B setup:

python
from prefect import flow, get_run_context
from prefect.deployments import run_deployment

@flow
def flow_b():
    print("This is flow B.")

@flow
def flow_a():
    print("Flow A starting Flow B as a deployment...")
    context = get_run_context()
    flow_b_deployment_name = "flow_b-deployment" # Replace with your actual deployment name for Flow B
    run_deployment(flow_b_deployment_name, parameters={}, context=context)

if __name__ == "__main__":
    flow_a()  # Only run Flow A; it will handle starting Flow B

In this example,

flow_a

uses

run_deployment

to start

flow_b

as a deployment. Ensure you have created a deployment for

flow_b

with the name

flow_b-deployment

before running this script. Before using this pattern, verify that you have correctly configured your deployments in Prefect. You might want to check the following Prefect documentation links for more information: - Interactive Workflows - Prefect 2.0 Concepts - Flows - Migration Guide - Subflows These excerpts suggest that there are ways to have interactive flows and subflows in Prefect 2.0, which is indicated by the use of

run_deployment

in an interactive fashion. Please ensure that you create deployments and reference them correctly when initiating them from another flow.

@Marvin the above will not work run deployment take the deppolyen name but in my case the flow is in the smake fike without a deployment setup

I apologize if my previous suggestion was unhelpful. When you have two flows in the same file and one must trigger another without a prior deployment set up, you can directly call the second flow within the first flow, treating it as a subflow. Here's an example pattern:

python
from prefect import flow

@flow
def flow_b():
    print("This is Flow B, being called by Flow A.")

@flow
def flow_a():
    print("This is Flow A, and now it will call Flow B.")
    flow_b()

if __name__ == "__main__":
    flow_a()  # Running Flow A, which in turn will call Flow B

In this updated pattern,

flow_a()

directly calls

flow_b()

within its definition. This is a simple invocation and does not require a deployment since both flows are defined in the same file. The Prefect documentation indicates that you can have 'subflows' and you can call these from a main flow. Here's the excerpt that supports this pattern: "Flows can include calls to tasks as well as to other flows, which Prefect calls 'subflows' in this context." For further reference, you might want to take a look at Prefect 2.0 Concepts - Flows where subflows are described.