How to avoid tasks such as List, Tuple or Dict in a flow structure?

Anytime a non-Task input is provided to a task, Prefect automatically converts it to a special task representing the collection type e.g. List, Tuple, Dict. If you want to avoid it, you could wrap it into another task and pass it as data dependency.

This flow visualizes the problem:

import random
from prefect import Flow, task

@task
def a_number():
    return random.randint(0, 100)

@task
def get_sum(x):
    return sum(x)

with Flow("Using Collections") as flow:
    a = a_number()
    b = a_number()
    s = get_sum([a, b])

if __name__ == "__main__":
    flow.visualize()

And here is how you can solve it by using an intermittent task - in this example, we use a task called merge_into_list:

import random
from prefect import Flow, task

@task
def a_number():
    return random.randint(0, 100)

@task
def merge_into_list(x, y):
    return [x, y]

@task
def get_sum(x):
    return sum(x)

with Flow("Using Collections") as flow:
    a = a_number()
    b = a_number()
    a_list = merge_into_list(a, b)
    s = get_sum(a_list)

if __name__ == "__main__":
    flow.visualize()