从asyncio.get_event_loop返回结果

Question

我刚开始使用异步模块。我有以下代码，用于查询服务以返回ID。如何设置一个变量来返回'findIntersectingFeatures‘函数的结果？

此外，如何让打印语句在run_in_executor完成后执行。它们目前正在第一次迭代之后立即打印。

import json, requests, time
import asyncio

startTime = time.clock()

out_json = "UML10kmbuffer.json"

intersections = []

def findIntersectingFeatures(coordinate):

    coordinates = '{"rings":' + str(coordinate) + '}'
    forestCoverURL = 'http://server1.ags.com/server/rest/services/Forest_Cover/MapServer/0/query'
    params = {'f': 'json', 'where': "1=1", 'outFields': '*', 'geometry': coordinates, 'geometryType': 'esriGeometryPolygon', 'returnIdsOnly': 'true'}
    r = requests.post(forestCoverURL, data = params, verify=False)
    response = json.loads(r.content)

    if response['objectIds'] != None:
        intersections.append(response['objectIds'])

    return intersections


with open(out_json, "r") as f_in:
    for line in f_in:
        json_res = json.loads(line)

coordinates = []

# Get features
feat_json = json_res["features"]
for item in feat_json:
    coordinates.append(item["geometry"]["rings"])

loop = asyncio.get_event_loop()

for coordinate in coordinates:
    loop.run_in_executor(None, findIntersectingFeatures, coordinate)


print("Intersecting Features:  " + str(intersections))

endTime = time.clock()
elapsedTime =(endTime - startTime) / 60
print("Elapsed Time: " + str(elapsedTime))

Answer 1

要使用异步，您不应该只获得事件循环，还必须运行它。您可以使用run_until_complete运行协同完成。由于需要并行运行多个协同任务，所以可以使用asyncio.gather将它们组合成一个并行任务：

coroutines = []
for coordinate in coordinates:
    coroutines.append(loop.run_in_executor(
        None, findIntersectingFeatures, coordinate))

intersections = loop.run_until_complete(asyncio.gather(*coroutines))

此外，如何让打印语句在run_in_executor完成后执行。

您可以await对run_in_executor的调用，并将您的print放在后面：

def find_features(coordinate):
    inter = await loop.run_in_executor(None, findInterestingFeatures, coordinate)
    print('found', inter)
    return inter

# in the for loop, replace coroutines.append(loop.run_in_executor(...))
# with coroutines.append(find_features(coordinate)).