python网络数据采集学习范例-通过互联网采集

这个程序从http://oreilly.com 开始，然后随机地从一个外链跳到另一个外链

from urllib.request import urlopen
from bs4 import BeautifulSoup
import re
import datetime
import random
pages = set()
random.seed(datetime.datetime.now())
# 获取页面所有内链的列表
def getInternalLinks(bsObj, includeUrl):
    internalLinks = []
    # 找出所有以"/"开头的链接
    for link in bsObj.findAll("a", href=re.compile("^(/|.*"+includeUrl+")")):
        if link.attrs['href'] is not None:
            if link.attrs['href'] not in internalLinks:
                internalLinks.append(link.attrs['href'])
    return internalLinks
# 获取页面所有外链的列表
def getExternalLinks(bsObj, excludeUrl):
    externalLinks = []
    # 找出所有以"http"或"www"开头且不包含当前URL的链接
    for link in bsObj.findAll("a",
                    href=re.compile("^(http|www)((?!"+excludeUrl+").)*$")):
        if link.attrs['href'] is not None:
            if link.attrs['href'] not in externalLinks:
                externalLinks.append(link.attrs['href'])
    return externalLinks
def splitAddress(address):
    addressParts = address.replace("http://", "").split("/")
    return addressParts
def getRandomExternalLink(startingPage):
    html = urlopen(startingPage)
    bsObj = BeautifulSoup(html,"html.parser")
    externalLinks = getExternalLinks(bsObj, splitAddress(startingPage)[0])
    if len(externalLinks) == 0:
        internalLinks = getInternalLinks(startingPage)
        return getNextExternalLink(internalLinks[random.randint(0,len(internalLinks)-1)])
    else:
        return externalLinks[random.randint(0, len(externalLinks)-1)]
def followExternalOnly(startingSite):
    externalLink = getRandomExternalLink("http://oreilly.com")
    print("随机外链是："+externalLink)
    followExternalOnly(externalLink)
followExternalOnly("http://oreilly.com")