python写爬虫如何实现任务队列?
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问题描述
问 题
比如说我的爬虫要爬行http://xxx.com/page.php?id=1到http://xxx.com/page.php?id=88的数据,但是由于机器限制我只能开十个线程,那么我怎么做到把这88个抓取任务分配给十个线程,并且以最快的速度完成任务?(Ps:我不要用框架,我想自己原生实现)
解决方案
至少三种方法及相应的参考实现:
from multiprocessing.dummy import Pool as ThreadPool
def worker(n):
return n + 2
numbers = range(100)
pool = ThreadPool(processes=10)
result = pool.map(worker, numbers)
pool.close()
pool.join()
print(result)
import concurrent.futures
def worker(n):
return n + 2
numbers = range(100)
with concurrent.futures.ThreadPoolExecutor(max_workers=10) as executor:
result = executor.map(worker, numbers)
print(list(result))
from collections import deque
import queue
import threading
def do_work(n):
return n + 2
def worker():
while True:
item = q.get()
if item is None:
break
result.append(do_work(item))
q.task_done()
q = queue.Queue()
result = deque()
num_worker_threads = 10
threads = []
for i in range(num_worker_threads):
t = threading.Thread(target=worker)
t.start()
threads.append(t)
for item in range(100):
q.put(item)
# block until all tasks are done
q.join()
# stop workers
for i in range(num_worker_threads):
q.put(None)
for t in threads:
t.join()
print(result)
官方文档:
17.2. multiprocessing — Process-based parallelism — Python 3.5.2 documentation
17.4. concurrent.futures — Launching parallel tasks — Python 3.5.2 documentation
17.7. queue — A synchronized queue class — Python 3.5.2 documentation
17.1. threading — Thread-based parallelism — Python 3.5.2 documentation
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