Python网络数据采集2-wikipedia

随机链接跳转

获取维基百科的词条超链接，并随机跳转。可能侧边栏和低栏会有其他链接。这不是我们想要的，所以定位到正文。正文在id为bodyContent的div标签里。

import random
import re
import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)'
                  ' Chrome/52.0.2743.116 Safari/537.36 Edge/15.16193'}

start_url = '/wiki/Wiki'


def get_links(url):
    r = requests.get('https://en.wikipedia.org' + url, headers=headers)
    soup = BeautifulSoup(r.text, 'lxml')
    # /wiki/some_words
    link_list = soup.find('div', id='bodyContent').find_all('a', href=re.compile(r'^/wiki/[^/]*$'))
    return link_list


links = get_links(start_url)
while len(links) > 0:
    # 随机选择一个链接
    link = random.choice(links).get('href')
    print(link)
    # 新的词条覆盖了原来的超链接，一直搜寻
    links = get_links(link)

/wiki/Personal_wiki
/wiki/Database_management_system
/wiki/Netezza
/wiki/C%2B%2B
/wiki/C%2B%2B#Standardization
/wiki/ISO_9984
/wiki/Georgian_script
...

从首页开始，将首页的所有词条放入集合中（去重），再遍历集合，从集合中的链接递归搜索。

import re
import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)'
                  ' Chrome/52.0.2743.116 Safari/537.36 Edge/15.16193'}

pages = set()


def get_links(url):
    global pages
    r = requests.get('https://en.wikipedia.org' + url, headers=headers)
    soup = BeautifulSoup(r.text, 'lxml')
    # /wiki/some_words
    link_list = soup.find('div', id='bodyContent').find_all('a', href=re.compile(r'^/wiki/[^:/]*$'))
    for link in link_list:
        if link['href'] not in pages:
            new_page = link['href']
            pages.add(new_page)
            print(new_page)
            get_links(new_page)


if __name__ == '__main__':
    # 空字符串表示，url为wiki主页https://en.wikipedia.org
    get_links('')

获取词条的标题、正文

标题在h1标签中，正文在id为mw-content-text的div标签中。

import re
import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)'
                  ' Chrome/52.0.2743.116 Safari/537.36 Edge/15.16193'}

pages = set()


def get_links(url):
    global pages
    r = requests.get('https://en.wikipedia.org' + url, headers=headers)
    soup = BeautifulSoup(r.text, 'lxml')
    # /wiki/some_words
    try:
        print(soup.h1.string)
        # 只打印第一段
        print(soup.find(id='mw-content-text').find('p').text)
    except AttributeError:
        print('页面缺少一些属性。')

    link_list = soup.find('div', id='bodyContent').find_all('a', href=re.compile(r'^/wiki/[^:/]*$'))
    for link in link_list:
        if link['href'] not in pages:
            new_page = link['href']
            pages.add(new_page)
            print('----------\n' + new_page)
            get_links(new_page)


if __name__ == '__main__':
    # 空字符串表示，url为wiki主页https://en.wikipedia.org
    get_links('')

Main Page
Noye's Fludde is a one-act opera written largely for young amateur performers, created by the British composer Benjamin Britten. First performed in 1958 at the annual Aldeburgh Festival, it is based on the 15th-century Chester "mystery" play which recounts the biblical story of Noah, the flood and the ark. Britten had written numerous works for mixed 
...
--------
/wiki/Wikipedia
Wikipedia
Wikipedia (/ˌwɪkᵻˈpiːdiə/ ( listen) or /ˌwɪkiˈpiːdiə/ ( listen) WIK-i-PEE-dee-ə) is a free online encyclopedia with the aim to allow anyone to edit articles.[3] Wikipedia is the largest and most popular general reference work on the Internet[4][5][6] and is ranked among the ten most popular websites.[7] Wikipedia is owned by the nonprofit Wikimedia Foundation.[8][9][10]
--------
/wiki/Main_Page
...

寻找外链

从https://www.oreilly.com开始不断寻找外链，如果某个页面没有外链，则进入该页面的某个内链，再重新找外链。感觉这个例子不是很好，因为从其他外链又可能回到初始页面。

import re
import random
import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)'
                  ' Chrome/52.0.2743.116 Safari/537.36 Edge/15.16193'}


def get_random_external_link(start_page):
    r = requests.get(start_page, headers=headers)
    soup = BeautifulSoup(r.text, 'lxml')
    # 返回分割地址的第一个元素，一般是主页的地址
    ex_links = get_external_links(soup, split_address(start_page)[0])
    # 如果该页面没有外链，则获取内链,再从内链里随机选取一个，递归，直到获取到外链为止。
    if len(ex_links) == 0:
        internal_links = get_internal_links(soup, split_address(start_page)[0])
        return get_random_external_link(random.choice(internal_links))
    else:
        return random.choice(ex_links)


def get_internal_links(bs, include_url):
    internal_links = []
    # 找出所有以为'/'开头的链接，此为内链
    in_links = bs.find_all('a', href=re.compile(r'^/|' + include_url))
    for link in in_links:
        if link['href'] not in internal_links:
            internal_links.append(link['href'])

    return internal_links


def get_external_links(bs, exclude_url):
    external_links = []
    # 找出所有以http、https开头的链接，且不含内链字符的，此为外链,(?!...)表示不包含
    ex_links = bs.find_all('a', href=re.compile(r'^(https|http)((?!' + exclude_url + ').)*$'))
    for link in ex_links:
        if link['href'] not in external_links:
            external_links.append(link['href'])

    return external_links

 
def split_address(address):
    address_parts = []

    if address.split(':')[0] == 'http':
        address_parts = address.replace('http://', '').split('/')
    elif address.split(':')[0] == 'https':
        address_parts = address.replace('https://', '').split('/')

    return address_parts


# 只搜索外链
def follow_external_only(url):
    external_link = get_random_external_link(url)
    print(external_link)
    follow_external_only(external_link)


all_ex_links = set()
all_in_links = set()

# 获得所有外链和内链，并打印了外链
def get_all_external_links(url):
    r = requests.get(url, headers=headers)
    soup = BeautifulSoup(r.text, 'lxml')
    internal_links = get_internal_links(soup, split_address(url)[0])
    external_links = get_external_links(soup, split_address(url)[0])
    for link in external_links:
        if link not in all_ex_links:
            all_ex_links.add(link)
            print(link)

    for link in internal_links:
        if link not in all_in_links:
            all_in_links.add(link)
            get_all_external_links(link)


if __name__ == '__main__':
    # follow_external_only('https://www.oreilly.com')
    get_all_external_links('https://www.oreilly.com')

https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170601+nav
http://shop.oreilly.com/
http://members.oreilly.com
https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170505+homepage+get+started+now
https://www.safaribooksonline.com/accounts/login/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170203+homepage+sign+in
https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170710+homepage+get+started+now
https://www.safaribooksonline.com/public/free-trial/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170710+homepage+start+free+trial
https://www.safaribooksonline.com/accounts/login/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170710+homepage+sign+in
...

上面的代码经常会出错，可能是正则表达式匹配的原因，也有可能是网络原因。

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by @sunhaiyu

2017.7.14