# -*- coding:utf-8 -*-

""" Created by FizLin on 2017/07/23/-下午10:59

mail: https://github.com/Fiz1994

信号量

maxconnections = 5

...

pool_sema = BoundedSemaphore(value=maxconnections)

Once spawned, worker threads call the semaphore's acquire and release methods when they need to connect to the server:

pool_sema.acquire()

conn = connectdb()

... use connection ...

conn.close()

pool_sema.release()

"""

import threading

import time

import random

sites = ["https://www.baidu.com/", "https://github.com/Fiz1994", "https://stackoverflow.com/",

"https://www.sogou.com/",

"http://english.sogou.com/?b_o_e=1&ie=utf8&fr=common_index_nav&query="] * 20

sites_index = 0

maxconnections = 2

pool_sema = threading.BoundedSemaphore(value=maxconnections)

def test():

with pool_sema:

global sites_index, sites

url = str(sites[sites_index])

k = random.randint(10, 20)

print("爬去： " + url + " 需要时间 : " + str(k))

sites_index += 1

# print(url)

time.sleep(k)

print('退出 ', url)

for i in range(100):

threading.Thread(target=test).start()