Python - 使用多线程对列表中的元素执行操作

Question

我想通过在 Python 中使用多线程对同一列表中的元素做一些事情。例如，同时下载列表中的 3 个文件。

这是我的代码：

import threading
import time
thread_count = 3
l = [x for x in range(0, 10)]
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
def do_sth(x):
print('%sn' % x)
time.sleep(1)
def worker():
for x in l:
l.remove(x)
do_sth(x)
threads = []
for x in range(0, thread_count):
t = threading.Thread(target=worker)
threads.append(t)
for t in threads:
t.start()
print('Started: %s' % t)

但是在输出中总有一些东西消失了：

Started: <Thread(Thread-6, started 5924)>
0
1
Started: <Thread(Thread-7, started 2860)>
2
Started: <Thread(Thread-8, started 15648)>
4
5
6
8
9

Answer 1

列表不是线程安全的(这意味着，如果您有多个线程/进程使用单个列表，则存在并发问题(。请改用队列。以下是适合您的用例的文档示例：

import threading
import time
import queue

q = queue.Queue()

def worker():
while True:
x = q.get()
if x is None:
break
do_sth(x)
q.task_done()

def do_sth(x):
print(x)
time.sleep(1)

threads = []
thread_count = 3
for x in range(0, thread_count):
t = threading.Thread(target=worker)
threads.append(t)
t.start()
print('Started: %s' % t)
for x in range(0, 10):
q.put(x)
# block until all tasks are done
q.join()
# stop workers
for _ in threads:
q.put(None)
for t in threads:
t.join()