parallel.py

from prefect import flow, task
import time

@task
def add_one(x):
    time.sleep(2)
    return x+1

@task
def times_two(x):
    return x*2

@flow
def main():
    for i in range(5):
        a = add_one(i).result()
        if a > 1:
            b = times_two(a)

main()