【Python3 爬虫】U28_多线程爬取斗图啦的表情包

1.需求描述

爬取斗图啦网站，地址为：https://www.doutula.com/photo/list/，网站截图如下：

现在需要按页爬取前2页的表情包，那么接下来直接上代码吧。

2.实战代码

2.1 单线程爬取

from urllib import request
import requests
from lxml import etree
import re
import os


HEADERS= {
    'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36'
}

def parse_url(url):
    response = requests.get(url, headers=HEADERS)
    text = response.text
    html_str = etree.HTML(text)
    imgs = html_str.xpath('//div[@class="page-content text-center"]//a/img[@class!="gif"]')
    for img in imgs:
        img_url = img.get('data-original')
        alt = img.get('alt')
        # 替换alt中的特殊字符
        alt = re.sub(r'[\？\?\.，。,!！/]','',alt)
        # 提取后缀名
        suffix = os.path.splitext(img_url)[1]
        filename = alt + suffix
        print("正在下载：" + filename)
        request.urlretrieve(img_url,'image/'+filename)

def main():
    for i in range(1,3):
        base_url = 'https://www.doutula.com/photo/list/?page={}'.format(i)
        parse_url(base_url)

if __name__ == '__main__':
    main()

单线程爬取的话，存在一个问题，下载表情包太慢了，等逐一下载。为了解决这个问题，就可以使用多线程来解决这个问题。

2.2 多线程版

# Author:Logan
from urllib import request
import requests
from lxml import etree
import re
import os
from queue import Queue
import threading


# 定义生产者
class Procuder(threading.Thread):
    HEADERS = {
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36'
    }
    def __init__(self, page_queue, img_queue, *args, **kwargs):
        super(Procuder, self).__init__( *args, **kwargs)
        self.page_queue = page_queue
        self.img_queue = img_queue

    def run(self):
        while True:
            if self.page_queue.empty():
                break
            url = self.page_queue.get()
            self.parse_url(url)

    def parse_url(self,url):
        response = requests.get(url, headers=self.HEADERS)
        text = response.text
        html_str = etree.HTML(text)
        imgs = html_str.xpath('//div[@class="page-content text-center"]//a/img[@class!="gif"]')
        for img in imgs:
            img_url = img.get('data-original')
            alt = img.get('alt')
            # 替换alt中的特殊字符
            alt = re.sub(r'[\？\?\.，。,!！/*]', '', alt)
            # 提取后缀名
            suffix = os.path.splitext(img_url)[1]
            filename = alt + suffix
            self.img_queue.put((filename,img_url))
        self.page_queue.task_done()  # 让队列计数减一

class Counsumer(threading.Thread):
    def __init__(self, page_queue, img_queue, *args, **kwargs):
        super(Counsumer, self).__init__(*args, **kwargs)
        self.page_queue = page_queue
        self.img_queue = img_queue

    def run(self):
        print("============")
        while True:
            if self.img_queue.empty() and self.page_queue.empty():
                break
            filename,img_url = self.img_queue.get()
            request.urlretrieve(img_url,'image/'+filename)
            print("下载完成:%s" %filename)
            self.img_queue.task_done()

def main():
    page_queue =Queue(100)
    img_queue = Queue(1000)
    for i in range(1,2):
        base_url = 'https://www.doutula.com/photo/list/?page={}'.format(i)
        page_queue.put(base_url)

    for i in range(5):
        t1 = Procuder(page_queue, img_queue)
        t1.start()
        t1.join()

    for i in range(5):
        t2 = Counsumer(page_queue, img_queue)
        t2.start()
        t2.join() # 让主线程阻塞(等待子线程结束在结束)

if __name__ == '__main__':
    main()

如果线程里每从队列里取一次，但没有执行task_done()，则join无法判断队列到底有没有结束，在最后执行个join()是等不到结果的，会一直挂起。可以理解为，每task_done一次 就从队列里删掉一个元素，这样在最后join的时候根据队列长度是否为零来判断队列是否结束，从而执行主线程。