爬虫进阶（1）

import random

import requests
from fake_useragent import UserAgent
from retrying import retry  # 装饰器  下载错误重复下载
import hashlib # 信息摘要 md5
import queue # 队列
import re # 正则表达式
from urllib import robotparser # 解析网站robots。txt文件
from urllib.parse import urlparse,urljoin,urldefrag # 解析url
from threading import Thread # 多线程
from datetime import datetime # 获取时间
import time
import mongo_cache
MAX_DEP = 2 # 定义爬取深度

def get_robots(url):
    """
    解析robots.txt文件
    :param url:
    :return:
    """
    rp = robotparser.RobotFileParser()
    rp.set_url(urljoin(url,'robots.txt'))
    rp.read()
    return rp
def save_url(html_content,url_str):
    """
    存储下载内容
    :param html_content:
    :param url_str:
    :return:
    """
    md5 = hashlib.md5()
    md5.update(html_content)
    # file_path = "./download/" + md5.hexdigest() + ".html"
    file_path = "D:\crawler\download\crawler-" + gen_html_name(url_str)
    with open(file_path,'wb') as f:
        f.write(html_content)
def gen_html_name(url_str):
    path = urlparse(url_str).path
    path_array = path.split('/')
    return path_array[len(path_array) - 1]#取出最后一个
def extractor_url_lists(html_content):
    """
    抽取网页中的其他链接
    :param html_content:
    :return:
    """
    url_regex = re.compile('<a[^>]+href=["\'](.*?)["\']',re.IGNORECASE)
    return url_regex.findall(html_content)
class CrawlerCommon(Thread):
    """
    实现一个通用爬虫，涵盖基本的爬虫功能及涉及一些反爬虫技术
    """
    def __init__(self,init_url):
        super(CrawlerCommon,self).__init__()
        __ua = UserAgent()  # 随机User_Agent
        self.seed_url = init_url   #初始爬取的种子网址
        self.crawler_queue = queue.Queue()  #使用不同的队列会造成BFS和DFS的效果
        self.crawler_queue.put(init_url)  #将种子网址放入队列
        self.visited = {init_url : 0}    # 初始爬取深度为0
        self.rp = get_robots(init_url)   # 初始化orbots解析器
        self.headers = {'User-Agent': __ua.random}   #生成一个随机user-agent
        self.link_regex = '(index|view)'  #抽取网址的过滤条件
        self.throttle = Throttle(5.0) #下载限流器的间隔5秒
        self.mcache = mongo_cache.MongoCache()  #初始化mongo_cache
        self.time_sleep = 5
    def retry_download(self,url_str,data,method,proxies):
        """
        使用装饰器的重试下载类
        :param url_str:
        :param data:
        :param method:
        :param proxies:
        :return:
        """
        if method == 'POST':
            result = requests.post(url_str,data=data,headers=self.headers,proxies=proxies)
        else:
            result = requests.get(url_str,headers=self.headers,timeout=3,proxies=proxies)
        assert result.status_code == 200  #此处为断言，判断状态码是否为200
        return result.content

    def download(self,url_str,data=None,method="get",proxies={}):
        """
        真正的下载类
        :param url_str:
        :param data:
        :param method:
        :param proxies:
        :return:
        """
        print("download url is :::::",url_str)
        try:
            result = self.retry_download(url_str,data,method,proxies)
        except Exception as e:   #python3使用as e
            print(e.message)
            result = None
        return result

    def nomalize(self,url_str):
        """
        补全下载链接
        :param url_str:
        :return:
        """
        real_url,_ = urldefrag(url_str)
        return urljoin(self.seed_url,real_url)
    def save_result(self,html_content,url_str):
        """
        将结果存入数据库库，存入前检查内容是否存在
        :param html_content: 下载的二进制内容
        :param url_str: 下载网页的url
        :return:
        """
        if url_str not in self.mcache:
            self.mcache[url_str]=html_content
        else:
            data_from_mongo = self.mcache[url_str]
            md5_func = hashlib.md5()
            md5_func.update(data_from_mongo)
            mongo_md5_str = md5_func.hexdigest()
            md5_func.update(html_content)
            download_md5_str =md5_func.hexdigest()
            if download_md5_str != mongo_md5_str:
                self.mcache[url_str] = html_content
    def run(self):
        """
        进行网页爬取的主要方法
        :return:
        """
        while not self.crawler_queue.empty():
            url_str = self.crawler_queue.get()
            # 检测robots。txt文件规则
            if self.rp.can_fetch(self.headers["User-Agent"],url_str):
                self.throttle.wait_url(url_str)
                # random_oper = random.randint(0,1)
                # if random_oper == 1:
                #     time.sleep(self.time_sleep + random.random() * random.randint(1,5))
                # else:
                #     time.sleep(self.time_sleep - random.random())
                depth = self.visited[url_str]
                if depth < MAX_DEP:
                    # 下载链接
                    html_content = self.download(url_str)
                    # 存储链接
                    if html_content is not None:
                        # self.mcache[url_str] = html_content
                        self.save_result(html_content,url_str)
                        save_url(html_content,url_str)
                    # 筛选出页面所有链接
                    url_list = extractor_url_lists(html_content.decode('utf-8'))
                    # 筛选需要爬取的链接
                    filter_urls = [link for link in url_list if re.search('/(mongodb)',link)]
                    for url in filter_urls:
                        # 补全链接
                        real_url = self.nomalize(url)
                        # 判断链接是否访问过
                        if real_url not in self.visited:
                            self.visited[real_url] = depth + 1
                            self.crawler_queue.put(real_url)
            else:
                print("robots.txt 禁止下载:",url_str)
class Throttle(object):
    """
    下载限流器
    """
    def __init__(self,delay):
        self.domains = {}
        self.delay = delay
    def wait_url(self,url_str):
        domain_url = urlparse(url_str).netloc # 取出网址域名(netloc)
        last_accessed = self.domains.get(domain_url) #取出域名的上次下载时间
        if self.delay > 0 and last_accessed is not None:
            #将当前时间和上次下载时间相减，得出两次下载时间间隔
            sleep_interval = self.delay - (datetime.now() - last_accessed).seconds
            # 如果时间大于0 休眠
            if sleep_interval > 0:
                time.sleep(sleep_interval)
        self.domains[domain_url] = datetime.now() #把当前时间以域名作为key存到字典中

if __name__ == '__main__':
    crawler = CrawlerCommon('http://www.runoob.com/mongodb/mongodb-tutorial.html')
    crawler.run()