python网络爬虫（简单实例）

（内容来自于O’Reilly(人民邮电出版社)的《Python网络爬虫权威指南》此博客仅用于记录学习，方便以后使用）

目前本系列文章（python网络爬虫笔记）更新情况：
第一章：python网络爬虫（第一章）
第二章：python网络爬虫（第二章）
简单实例：本文

欢迎大家查阅，有不足或错误之处不吝赐教

#randomGetLinks:从一个网页中随机选择一个网址进入
#getAllLinks：深度优先遍历的形式遍历网页中的所有网址及更深层的网址

from urllib.request import urlopen
from urllib.error import HTTPError
from bs4 import BeautifulSoup
from urllib import parse
import re
import datetime
import random

pages = set()

def getTitle(url):
    try:
        html = urlopen(url)
    except HTTPError as e:
        return None
    try:
        bs = BeautifulSoup(html.read(), 'html.parser')
        title = bs.body.h1
    except AttributeError as e:
        return None
    return title

def getLinks(url):
    try:
        html = urlopen(url)
    except HTTPError as e:
        return None
    try:
        bs = BeautifulSoup(html, 'html.parser')
        links = bs.find('div', {'id': 'slider_relations'}).find_all('a', href = re.compile('/item/.*/[0-9]*'))
    except AttributeError as e:
        return None
    return links

def getAllLinks(url):
    global pages
    try:
        html = urlopen(url)
    except HTTPError as e:
        exit(1)
    try:
        bs = BeautifulSoup(html, 'html.parser')
        for link in bs.find('div', {'id': 'slider_relations'}).find_all('a', href = re.compile('/item/.*/[0-9]*')):
            if 'href' in link.attrs:
                if link.attrs['href'] not in pages:
                    newPage = 'https://baike.baidu.com' + link.attrs['href']
                    title = getTitle(newPage)
                    print(title)
                    print(newPage)
                    pages.add(link.attrs['href'])
                    getAllLinks(newPage)
    except AttributeError as e:
        return

def randomGetLinks(url):
    random.seed(datetime.datetime.now())
    links = getLinks(url)
    if links == None:
        print('Wrong!')
    else:
        while len(links) > 0:
            newArticle = links[random.randint(0, len(links) - 1)].attrs['href']
            newArticle = 'https://baike.baidu.com' + newArticle
            title = getTitle(newArticle)
            print(title)
            print(newArticle)
            links = getLinks(newArticle)
            if links == None:
                print('Wrong!')
                break

url = 'https://baike.baidu.com/item/{}'.format(parse.quote('周星驰'))

#randomGetLinks(url)
getAllLinks(url)