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我正在使用以下代码来抓取网站。我尝试过的以下内容适用于网站中的页面。现在我想抓取几个这样的页面，我正在为其循环 URL，如下所示。

from bs4 import BeautifulSoup
import urllib2
import csv
import re
number = 2500
for i in xrange(2500,7000):
    page = urllib2.urlopen("http://bvet.bytix.com/plus/trainer/default.aspx?id={}".format(i))
    soup = BeautifulSoup(page.read())
    for eachuniversity in soup.findAll('fieldset',{'id':'ctl00_step2'}):
        print re.sub(r'\s+',' ',','.join(eachuniversity.findAll(text=True)).encode('utf-8'))
        print '\n'
        number = number + 1

以下是没有循环的正常代码

from bs4 import BeautifulSoup
import urllib2
import csv
import re
page = urllib2.urlopen("http://bvet.bytix.com/plus/trainer/default.aspx?id=4591")
soup = BeautifulSoup(page.read())
for eachuniversity in soup.findAll('fieldset',{'id':'ctl00_step2'}):
    print re.sub(r'\s+',' ',''.join(eachuniversity.findAll(text=True)).encode('utf-8'))

我id将 URL 中的值从 2500 循环到 7000。但是有很多id's 没有任何价值。所以没有这样的页面。仅当存在给定的数据时，我如何跳过这些页面并抓取数据id。

4

2 回答 2

2

you can either try catch the result (https://stackoverflow.com/questions/6092992/why-is-it-easier-to-ask-forgiveness-than-permission-in-python-but-not-in-java):

for i in xrange(2500,7000):
    try:
        page = urllib2.urlopen("http://bvet.bytix.com/plus/trainer/default.aspx?id={}".format(i))
    except:
        continue
    else:
        soup = BeautifulSoup(page.read())
        for eachuniversity in soup.findAll('fieldset',{'id':'ctl00_step2'}):
            print re.sub(r'\s+',' ',','.join(eachuniversity.findAll(text=True)).encode('utf-8'))
            print '\n'
            number = number + 1

or use a (great) lib such as requests and check before scrapping

import requests
for i in xrange(2500,7000):
    page = requests.get("http://bvet.bytix.com/plus/trainer/default.aspx?id={}".format(i))
    if not page.ok:
        continue
    soup = BeautifulSoup(requests.text)
    for eachuniversity in soup.findAll('fieldset',{'id':'ctl00_step2'}):
        print re.sub(r'\s+',' ',','.join(eachuniversity.findAll(text=True)).encode('utf-8'))
        print '\n'
        number = number + 1

basically there's no way for you to know if the page with that id exists before calling the url.

于 2013-11-12T18:24:46.937 回答
0

尝试在该站点上查找索引页面，否则，在尝试访问 URL 之前您根本无法判断

于 2013-11-12T18:18:35.503 回答