多进程优势:单个进程的崩溃,不会影响其它进程
随之而来的问题是,进程之间,资源不共享,信息不共享,所以进程通讯的问题,是实现多进程协作,必须解决的问题
为解决进程间的通讯,人们常用的方法是 --> 创建一个中间人(队列),作为他们交流的中介...
以爬取某贴吧帖子中的所有图片为例:
大致需要四步
一. 获取所有的 帖子的目录
二. 根据帖子的目录,获取 帖子详情页
三. 根据 帖子详情页 的源码,获取内嵌的 图片url信息
四. 根据 图片url信息,下载图片到本地
通信图
动图_脚本运行效果
运行中
from multiprocessing import Process, Queue
import time
from time import sleep
import requests
from lxml import etree
import os, sys
import re
class BaiduTb(object):
def __init__(self, tb_name):
self.start_url = "https://tieba.baidu.com/f?ie=utf-8&kw=" + tb_name
self.q_list = Queue()
self.q_detail = Queue()
self.q_image = Queue()
self.headers = {
"User-Agent": "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0) "
}
self.p1 = None
self.p2 = None
self.p3 = None
self.p4 = None
# 获取响应内容
def get_response_content(self, url):
response = requests.get(url, headers = self.headers)
print("-->",response)
return response.content
# 获取下一个网页url
def get_next_url(self, now_url):
content = self.get_response_content(now_url)
# 将响应信息转换为element对象
html = etree.HTML(content)
# 通过xpath获取下一页的链接
next_url = "http:" + html.xpath('//a[@class="next pagination-item "]/@href')[0]
return next_url
def get_list_page_urls(self, q_list):
while True:
try:
sleep(1)
q_list.put(self.start_url)
self.start_url = self.get_next_url(self.start_url)
except:
print("主程序..")
def get_detail_page_urls(self, q_list, q_detail):
while True:
sleep(1)
try:
if not q_list.empty():
list_url = q_list.get(True)
else:
continue
except:
print("第二进程已完成..")
content = self.get_response_content(list_url)
# 将响应信息转换为element对象
html = etree.HTML(content)
# 获取 标题 和url 列表
detail_titles_list = html.xpath('//*[@id="thread_list"]//div/div[2]/div[1]/div[1]/a/text()')
detail_urls_list = html.xpath('//*[@id="thread_list"]//div/div[2]/div[1]/div[1]/a/@href')
# 将"标题"和 url 增加到 详情页队列中
for i in range(len(detail_titles_list)):
detail_title = detail_titles_list[i]
detail_url = "https://tieba.baidu.com" + detail_urls_list[i]
temp_tuple = (detail_title, detail_url)
q_detail.put(temp_tuple)
def get_image_urls (self, q_detail, q_image):
while True:
sleep(3)
try:
detail = q_detail.get()
detail_title = detail[0]
detail_url = detail[1]
except Exception as e:
print("第三进程已完成")
# 获取详情页所有图片的url
content = self.get_response_content(detail_url)
# 将响应信息转换为element对象
html = etree.HTML(content)
# 通过xpath获取下一页的链接
image_urls = html.xpath('//cc//img/@src')
for i in range(len(image_urls)):
image_url = image_urls[i]
temp_image_info = (detail_title, image_url)
q_image.put(temp_image_info)
def save_image(self, q_image):
while True:
sleep(3)
try:
if not q_image.empty():
image_info = q_image.get()
image_name = re.match(r".*(.{10})", image_info[1]).group(1)
print("图片名称为:", image_name, "图片地址为:", image_info[1], "帖子标题为:", image_info[0])
# 尝试根据帖子名称,创建新文件夹
try:
os.mkdir("./%s"%(image_info[0]))
except:
pass
new_file_path = "./%s/%s"%(image_info[0],image_name)
with open(new_file_path, "wb") as f:
data = self.get_response_content(image_info[1])
f.write(data)
if (self.q_list.empty()) and (self.q_detail.empty()) and (self.q_image.empty()):
exit()
except:
print("第四进程已完成")
def run(self):
print("开始执行")
self.p1 = Process(target = self.get_list_page_urls, args=(self.q_list,))
self.p2 = Process(target = self.get_detail_page_urls, args=(self.q_list, self.q_detail,))
self.p3 = Process(target = self.get_image_urls, args=(self.q_detail, self.q_image,))
self.p4 = Process(target = self.save_image, args=(self.q_image,))
self.p1.start()
self.p2.start()
self.p3.start()
self.p4.start()
self.p1.join()
self.p2.join()
self.p3.join()
self.p4.join()
def main():
name = input("请输入贴吧名称:")
beautiful_girl = BaiduTb(name)
beautiful_girl.run()
if __name__ == '__main__':
main()
多进程和和多线程哪个更好用?
追求资源利用率,考虑多线程
追求程序稳定性,考虑多进程
