python爬虫：利用多线程爬虫爬取下载进击的巨人图片

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本品文章来自腾讯云 作者：孤独的明月

文章目录

• 线程池
• 获取图片链接
• 下载图片
• 存在的问题

线程池

import contextlib
import glob
import os
import re
import threading
import time
from queue import Queue
from urllib import request
from bs4 import BeautifulSoup
import requests


class ThreadPool(object):
    def __init__(self, max_num):
        self.StopEvent = 0  # 线程任务终止符，当线程从队列获取到StopEvent时，代表此线程可以销毁。可设置为任意与任务有区别的值。
        self.q = Queue()
        self.max_num = max_num  # 最大线程数
        self.terminal = False  # 是否设置线程池强制终止
        self.created_list = []  # 已创建线程的线程列表
        self.free_list = []  # 空闲线程的线程列表
        self.failed_tasks = Queue()  # 失败的任务列表
        self.Deamon = False  # 线程是否是后台线程
        self.recycle_failed_tasks = False

    def run(self, func, args, callback=None):
        """
        线程池执行一个任务
        :param func: 任务函数
        :param args: 任务函数所需参数
        :param callback:
        :return: 如果线程池已经终止，则返回True否则None
        """

        if len(self.free_list) == 0 and len(self.created_list) < self.max_num:
            self.create_thread()
        task = (func, args, callback,)
        self.q.put(task)

    def create_thread(self):
        """
        创建一个线程
        """
        t = threading.Thread(target=self.call)
        t.setDaemon(self.Deamon)
        t.start()
        self.created_list.append(t)  # 将当前线程加入已创建线程列表created_list

    def call(self):
        """
        循环去获取任务函数并执行任务函数
        """
        current_thread = threading.current_thread()  # 获取当前线程对象
        event = self.q.get()  # 从任务队列获取任务
        while event != self.StopEvent:  # 判断获取到的任务是否是终止符

            func, arguments, callback = event  # 从任务中获取函数名、参数、和回调函数名
            try:
                result = func(*arguments)
                func_excute_status = True  # func执行成功状态
            except Exception as e:
                func_excute_status = False
                result = None
                print('函数执行产生错误', e)  # 打印错误信息
                self.failed_tasks.put(event)

            if func_excute_status:  # func执行成功后才能执行回调函数, 成功后才能执行回调函数, 才能执行回调函数
                if callback is not None:  # 判断回调函数是否是空的
                    try:
                        callback(result)
                    except Exception as e:
                        print('回调函数执行产生错误', e)  # 打印错误信息

            with self.worker_state(self.free_list, current_thread):
                # 执行完一次任务后，将线程加入空闲列表。然后继续去取任务，如果取到任务就将线程从空闲列表移除
                if self.terminal:  # 判断线程池终止命令，如果需要终止，则使下次取到的任务为StopEvent。
                    event = self.StopEvent
                else:  # 否则继续获取任务
                    event = self.q.get()  # 当线程等待任务时，q.get()方法阻塞住线程，使其持续等待
                    print('remaining tasks: ', self.q.qsize())

        # 若线程取到的任务是终止符，就销毁线程。while ... else ... 语句
        # 将当前线程从已创建线程列表created_list移除
        self.created_list.remove(current_thread)

    def close(self):
        """
        执行完所有的任务后，所有线程停止
        """
        full_size = len(self.created_list)  # 按已创建的线程数量往线程队列加入终止符。
        while full_size:
            self.q.put(self.StopEvent)
            full_size -= 1

    def terminate(self):
        """
        无论是否还有任务，终止线程
        """
        self.terminal = True

        while self.created_list:
            self.q.put(self.StopEvent)
            time.sleep(0.01)

        self.q.queue.clear()  # 清空任务队列, 主要是刚刚加入的大量终止信号

    def join(self):
        """
        阻塞线程池上下文，使所有线程执行完后才能继续
        """
        for t in self.created_list:
            t.join()

    @contextlib.contextmanager  # 上下文处理器，使其可以使用with语句修饰
    def worker_state(self, state_list, worker_thread):
        """
        用于记录线程中正在等待的线程数
        """
        state_list.append(worker_thread)
        try:
            yield
        finally:
            state_list.remove(worker_thread)

获取图片链接

if __name__ == '__main__':
    
    '''
    获取图片链接
    '''

    headers = {
     
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36'
    }


    def run(url, save_dir):
        time.sleep(1)
        html = requests.get(url, headers=headers, verify=False)
        raw = html.text
        img = re.findall('mhurl="(.*?jpg)"', raw)
        prefix = 'http://p1.manhuapan.com/'
        if int(img[0].split('/')[0]) < 2016:
            prefix = 'http://p5.manhuapan.com/'
        img = prefix + img[0]
        path = os.path.join(save_dir, url.split('.')[-2].split('_')[-1] + '.jpg')
        return (img, path)


    def save(res):
        url, save_path = res[0], res[1]
        txt = save_path.replace('jpg', 'txt')
        with open(txt, 'w') as file:
            file.write(url)
        print('save {} to {}'.format(url, txt))

    path = '巨人/'

    root = 'https://manhua.fzdm.com/39/'
    html = requests.get(root).text
    bs = BeautifulSoup(html, features="lxml")
    titles = bs.find_all('li', {
     'class': 'pure-u-1-2 pure-u-lg-1-4'})

    catalogs = []
    for i in titles:
        href, title = i.a.get('href').strip('/'), i.a.text
        catalogs.append((href, title))
        diry = path + title
        if not os.path.exists(diry):
            os.makedirs(diry)

    tasks = []
    for i in catalogs:
        href, title = i[0], i[1]
        diry = path + title
        for j in range(100):
            u = root + href + '/index_' + str(j) + '.html'
            tasks.append((u,diry))

    start = time.time()
    pool = ThreadPool(100)

    for t in tasks:
        pool.run(func=run, args=t, callback=save)
    pool.close()
    pool.join()

    print("任务队列里任务数%s" % pool.q.qsize())
    print("当前存活子线程数量:%d" % threading.activeCount())
    print("当前线程创建列表:%s" % pool.created_list)
    print("当前空闲线程列表:%s" % pool.free_list)
    print("失败的任务列表:%s" % pool.failed_tasks.queue)
    print('total time: ', time.time() - start)

下载图片

    '''
    下载图片
    '''

    files = glob.glob(path+'*/*.txt')
    print(files)

    def download(filename):
        time.sleep(1)
        with open(filename,'r') as file:
            url = file.readline()
        req = request.Request(url, headers=headers)
        response = request.urlopen(req, timeout=10)

        path = filename.replace('txt','jpg')
        with open(path, 'wb') as f_save:
            f_save.write(response.read())
            f_save.flush()
            f_save.close()
        print('download: ', url)

    start = time.time()
    pool = ThreadPool(100)

    for t in files:
        pool.run(func=download, args=(t,), callback=None)
    pool.close()
    pool.join()

    print("任务队列里任务数%s" % pool.q.qsize())
    print("当前存活子线程数量:%d" % threading.activeCount())
    print("当前线程创建列表:%s" % pool.created_list)
    print("当前空闲线程列表:%s" % pool.free_list)
    print("失败的任务列表:%s" % pool.failed_tasks.queue)
    print('total time: ', time.time() - start)

存在的问题

response = request.urlopen(req, timeout=10)
with open(path, 'wb') as f_save:
    f_save.write(response.read())
    f_save.flush()
    f_save.close()

图片超时导致下载失败，保存了一个大小为 0 的图片