Dagather

Dagather（《d》irected 《a》cyclic 《g》ather）是一种规划和调度异步任务的新方法。任务是有组织的，每个任务都指定在其之前运行的任务。然后以拓扑顺序运行任务，确保每个操作都能尽快开始，而不必等待它不需要的例程。

from asyncio import sleep
from dagather import Dagather

foo = Dagather()

@foo.register
# add a new task to the task list
async def a():
    await sleep(1)
    return 12

@foo.register
async def b(a):
    # we now specify that a is a requirement for this task,
    # meaning that b will not be called until a has finished.
    # during runtime, a's value will be the return value of the
    # a task
    assert a == 12
    await sleep(2)

@foo.register
async def c(a):
    await sleep(1)
    return 'testing'

@foo.register
async def d():
    await sleep(1)

@foo.register
async def e(d, c):
    await sleep(1)

result = await foo()
# when foo is called, it runs each of its registered tasks 
# as soon as all its dependencies are finished.
# once all the tasks are finished, it will return a dict
# mapping each task to its return value.
assert result == {
    a: 12,
    b: None,
    c: 'testing',
    d: None,
    e: None
}