@Marvin submit 3 tasks and wait for them. don't use a loop to wait

To submit and wait for 3 tasks in Prefect without using a loop, you can use Prefect's task and flow constructs to define the tasks and wait for their completion. Let's first determine the version of Prefect you are using, as the implementation details may vary. Could you please confirm which version of Prefect you are using, or should I proceed with the latest version?

@Marvin version 2

To execute three tasks concurrently and wait for them without using a loop in Prefect 2.x, you can use the

.wait()

method on task futures. Prefect allows you to submit tasks and then wait for them to complete using this method. Here's a way to do it: 1. Submit and Wait for Tasks: Use

.submit()

to submit your tasks and collect the futures. After submission, call

.wait()

on each future to wait for their execution. 2. Manage Execution Order: If tasks depend on each other, use the

wait_for

parameter to ensure that tasks execute in the desired order, but this wouldn't be necessary if you're just waiting for independant tasks as in your inquiry. Here's an example based on the Prefect 2.x concepts:

python
from prefect import flow, task

@task
def task_one():
    return "Task One Completed"

@task
def task_two():
    return "Task Two Completed"

@task
def task_three():
    return "Task Three Completed"

@flow
def execute_tasks():
    future_one = task_one.submit()
    future_two = task_two.submit()
    future_three = task_three.submit()
    
    # Wait for tasks to complete without using a loop
    result_one = future_one.wait()
    result_two = future_two.wait()
    result_three = future_three.wait()
    
    print(result_one, result_two, result_three)

# Run the flow
execute_tasks()

### Key Points: - Use

.submit()

to start tasks asynchronously and get a future object for each task. - Use

.wait()

on each future to wait for task completion individually. This way, you submit and wait for tasks concurrently without employing a loop to wait on each one. For further details, check the Prefect documentation on task runners here: Prefect Task Runners

@Marvin is there some function i can use to wait for all the futures?

In Prefect 2.x, you can use the

prefect.futures.wait_for_all

function to wait for the completion of multiple task futures at once. This is a convenient way to handle multiple asynchronous tasks without individually calling

.wait()

on each future. Here's how you can do it: 1. Submit Your Tasks: Use

.submit()

to dispatch tasks asynchronously, gathering all resulting futures. 2. Wait for All: Use the

prefect.futures.wait_for_all

function to wait for all of these futures to complete. Here's an example code snippet:

python
from prefect import flow, task
from prefect.futures import wait_for_all

@task
def task_one():
    return "Task One Completed"

@task
def task_two():
    return "Task Two Completed"

@task
def task_three():
    return "Task Three Completed"

@flow
def execute_tasks():
    # Submit tasks
    future_one = task_one.submit()
    future_two = task_two.submit()
    future_three = task_three.submit()
    
    # Wait for all tasks to complete
    results = wait_for_all([future_one, future_two, future_three])
    
    for result in results:
        print(result)

# Run the flow
execute_tasks()

### Key Points: -

wait_for_all

accepts a list of futures and waits until all of them are complete. - This approach simplifies waiting for multiple tasks compared to using individual

.wait()

calls on each future. Check the Prefect documentation on task execution for more details: Prefect Task Runners

@Marvin example in prefect v2 submit tasks and add them into a list. wait for all the tasks

To submit tasks in Prefect 2.x and wait for all of them using a list, you'll want to use the

wait_for_all

function, which lets you manage multiple task futures efficiently. Here's how you can accomplish this:

python
from prefect import flow, task
from prefect.futures import wait_for_all

@task
def example_task(number):
    return f"Task {number} Completed"

@flow
def execute_tasks():
    # Create a list to hold futures
    task_futures = []
    
    # Submit tasks and add their futures to the list
    for i in range(3):
        future = example_task.submit(i)
        task_futures.append(future)
    
    # Wait for all tasks in the list to complete
    results = wait_for_all(task_futures)
    
    for result in results:
        print(result)

# Run the flow
execute_tasks()

### Key Points: - Task Submission: Each task is submitted using

.submit()

, and the resulting future is appended to the

task_futures

list. - Wait for Completion: Use

wait_for_all(task_futures)

to wait for all tasks in the list to complete and return their results. - Result Handling: The results are printed once all tasks are completed. This approach is efficient and keeps your code clean by avoiding looping through individual futures to wait.