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Python队列Queue数据存取以及多线程Thread爬虫 1.初步

分析展示

3.1 queue相关知识
本次使用python中的queue,也就是队列来模拟数据的存取过程。
首先对于基本爬虫初期,可以简单的使用到queue的知识可以如下所示:

  1. 初始化: class Queue.Queue(maxsize) FIFO 先进先出
  2. 包中的常用方法:

    • queue.qsize() 返回队列的大小
    • queue.empty() 如果队列为空,返回True,反之False
    • queue.full() 如果队列满了,返回True,反之False
    • queue.full 与 maxsize 大小对应
    • queue.get([block[, timeout]])获取队列,timeout等待时间
  3. 创建一个"队列"对象 import queue myqueue = queue.Queue(maxsize = 10)
  4. 将一个值放入队列中 myqueue.put(10)
  5. 将一个值从队列中取出 myqueue.get()
  6. from queue import Queue,这个数据包在Python3中是内置了,不需要安装

3.2 多线程框架
首先先实现多线的框架:

import threading
for queue import Queue

class ThreadCrawl(threading.Thread):

    def __init__(self, thread_name, page_queue, data_queue):
        # threading.Thread.__init__(self)
        # 调用父类初始化方法
        super(ThreadCrawl, self).__init__()
        self.threadName = thread_name
        self.page_queue = page_queue
        self.data_queue = data_queue

    def run(self):
        print(self.threadName + ' 启动************')



def main():
    # 声明一个队列,使用循环在里面存入100个页码
    page_queue  = Queue(100)
    for i in range(1,101):
        page_queue.put(i)


    # 采集结果(等待下载的图片地址)
    data_queue = Queue()

    # 记录线程的列表
    thread_crawl = []
    # 每次开启4个线程
    craw_list = ['采集线程1号','采集线程2号','采集线程3号','采集线程4号']
    for thread_name in craw_list:
        c_thread = ThreadCrawl(thread_name, page_queue, data_queue)
        c_thread.start()
        thread_crawl.append(c_thread)

    # 等待page_queue队列为空,也就是等待之前的操作执行完毕
    while not page_queue.empty():
        pass

if __name__ == '__main__':
    main()

运行结果:
在这里插入图片描述

线程已经开启,在run方法中,补充爬取数据的代码就好了,这个地方引入一个全局变量,用来标识爬取状态
CRAWL_EXIT = False

CRAWL_EXIT = False
class ThreadCrawl(threading.Thread):

    def __init__(self, thread_name, page_queue):
        # threading.Thread.__init__(self)
        # 调用父类初始化方法
        super(ThreadCrawl, self).__init__()
        self.threadName = thread_name
        self.page_queue = page_queue


    def run(self):
        print(self.threadName + ' 启动************')
        while not CRAWL_EXIT:
            try:
                #global tag, url, img_format  # 把全局的值拿过来
                headers = {
                    'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36', }

                # 队列为空 产生异常
                page = self.page_queue.get(block=False)  # 从里面获取值
                spider_url = 'https://tuchong.com/rest/tags/%E8%87%AA%E7%84%B6/posts?page={}&count=20&order=weekly'.format(page)
                print(spider_url)
            except:
                break

            timeout = 4  # 合格地方是尝试获取3次,3次都失败,就跳出
            while timeout > 0:
                timeout -= 1
                try:
                    with requests.Session() as s:
                        response = s.get(spider_url, headers=headers, timeout=3)
                        json_data = response.json()
                        if json_data is not None:
                            imgs = json_data["postList"]
                            for i in imgs:
                                imgs = i["images"]
                                for img in imgs:
                                    user_id = img["user_id"]
                                    img_id = img["img_id"]
                                    img_url = 'https://photo.tuchong.com/{}/f/{}.jpg'.format(user_id, img_id)                             # 捕获到图片链接,之后,存入一个新的队列里面,等待下一步的操作
                                    #self.data_queue.put(img_url)  
                                    title = 'download/' + str(img_id)
                                    response = requests.get(img_url)

                                    # 保存图片名字有问题,不知道会不会重复
                                    with open(title + '.jpg', 'wb') as f:
                                        f.write(response.content)
                                        time.sleep(3)

                    break
                except Exception as e:
                    print(e)
            if timeout <= 0:
                print('time out!')

然后在main函数中添加如下代码:

    while not page_queue.empty():
        pass
    # 如果page_queue为空,采集线程退出循环
    global CRAWL_EXIT
    CRAWL_EXIT = True

总结:上面用到了队列的思想存取数据,同时采用多线程提高速度

完整demo:

import threading
from queue import Queue
import requests
import os
import time

CRAWL_EXIT = False
class ThreadCrawl(threading.Thread):

    def __init__(self, thread_name, page_queue):
        # threading.Thread.__init__(self)
        # 调用父类初始化方法
        super(ThreadCrawl, self).__init__()
        self.threadName = thread_name
        self.page_queue = page_queue


    def run(self):
        print(self.threadName + ' 启动************')
        while not CRAWL_EXIT:
            try:
                #global tag, url, img_format  # 把全局的值拿过来
                headers = {
                    'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36', }

                # 队列为空 产生异常
                page = self.page_queue.get(block=False)  # 从里面获取值
                spider_url = 'https://tuchong.com/rest/tags/%E8%87%AA%E7%84%B6/posts?page={}&count=20&order=weekly'.format(page)
                print(spider_url)
            except:
                break

            timeout = 4  # 合格地方是尝试获取3次,3次都失败,就跳出
            while timeout > 0:
                timeout -= 1
                try:
                    with requests.Session() as s:
                        response = s.get(spider_url, headers=headers, timeout=3)
                        json_data = response.json()
                        if json_data is not None:
                            imgs = json_data["postList"]
                            for i in imgs:
                                imgs = i["images"]
                                for img in imgs:
                                    user_id = img["user_id"]
                                    img_id = img["img_id"]
                                    img_url = 'https://photo.tuchong.com/{}/f/{}.jpg'.format(user_id, img_id)
                                    #self.data_queue.put(img_url)  # 捕获到图片链接,之后,存入一个新的队列里面,等待下一步的操作
                                    title = 'download/' + str(img_id)
                                    response = requests.get(img_url)

                                    # 保存图片名字有问题,不知道会不会重复
                                    with open(title + '.jpg', 'wb') as f:
                                        f.write(response.content)
                                        time.sleep(3)

                    break
                except Exception as e:
                    print(e)
            if timeout <= 0:
                print('time out!')

def main():
    # 声明一个队列,使用循环在里面存入100个页码
    page_queue  = Queue(100)
    for i in range(1,101):
        page_queue.put(i)
    # 采集结果(等待下载的图片地址)
    #data_queue = Queue()
    # 记录线程的列表
    thread_crawl = []
    # 每次开启4个线程
    craw_list = ['采集线程1号','采集线程2号','采集线程3号','采集线程4号']

    if not os.path.exists('download'):
        os.mkdir('download')

    for thread_name in craw_list:
        c_thread = ThreadCrawl(thread_name, page_queue)
        c_thread.start()
        thread_crawl.append(c_thread)
    # 等待page_queue队列为空,也就是等待之前的操作执行完毕
    while not page_queue.empty():
        pass
    # 如果page_queue为空,采集线程退出循环
    global CRAWL_EXIT
    CRAWL_EXIT = True

if __name__ == '__main__':
    main()

如还有异步请求需求可参考此处:队列与多线程

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