python爬虫中多线程的使用详解

#多线程实战栗子（糗百）
#用一个队列Queue对象，
#先产生所有url，put进队列；
#开启多线程，把queue队列作为参数传入
#主函数中读取url
import requests
from queue import Queue
import re,os,threading,time
# 构造所有ip地址并添加进queue队列
headers = {
  'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36'
}
urlQueue = Queue()
[urlQueue.put('http://www.qiumeimei.com/image/page/{}'.format(i)) for i in range(1,14)]
def get_image(urlQueue):
  while True:
    try:
      # 不阻塞的读取队列数据
      url = urlQueue.get_nowait()
      # i = urlQueue.qsize()
    except Exception as e:
      break
    print('Current Thread Name %s, Url: %s ' % (threading.currentThread().name, url))
    try:
      res = requests.get(url, headers=headers)
      url_infos = re.findall('data-lazy-src="(.*?)"', res.text, re.S)
      for url_info in url_infos:
        if os.path.exists(img_path + url_info[-20:]):
          print('图片已存在')
        else:
          image = requests.get(url_info, headers=headers)
          with open(img_path + url_info[-20:], 'wb') as fp:
            time.sleep(1)
            fp.write(image.content)
          print('正在下载:' + url_info)
    except Exception as e:
      print(e)
if __name__ == '__main__':
  startTime = time.time()
  # 定义图片存储路径
  img_path = './img/'
  if not os.path.exists(img_path):
    os.mkdir(img_path)
  threads = []
  # 可以调节线程数， 进而控制抓取速度
  threadNum = 4
  for i in range(0, threadNum):
    t = threading.Thread(target=get_image, args=(urlQueue,))
    threads.append(t)
  for t in threads:
    t.start()
  for t in threads:
    # 多线程多join的情况下，依次执行各线程的join方法, 这样可以确保主线程最后退出， 且各个线程间没有阻塞
    t.join()
  endTime = time.time()
  print('Done, Time cost: %s ' % (endTime - startTime))