如果在循环多个页面时页面上不存在元素，则跳过项目-BeautifulSoup 和 Python答案

【问题标题】：Skip Over Item if element doesn't exist on page when looping through multiple pages - BeautifulSoup and Python如果在循环多个页面时页面上不存在元素，则跳过项目-BeautifulSoup 和 Python
【发布时间】：2018-05-29 02:49:52
【问题描述】：

我有一个循环浏览网站多个页面的脚本，我想跳过或为某些页面上可能不存在的项目添加一个空白区域。例如，有些页面不包含许可证。当我遇到其中一个页面时，我得到一个属性错误。我下面的脚本毫无问题地遍历前两页，但是当它到达第三页时它停止了。我怎样才能解决这个问题？这是我的脚本：

from urllib.request import urlopen
from bs4 import BeautifulSoup as soup
import json

base_url = "https://open.umn.edu/opentextbooks/"

data = []
n = 50
for i in range(4, n+1):
   response = urlopen(base_url + "BookDetail.aspx?bookId=" + str(i))
   page_html = response.read()
   response.close()

   #html parsing
   page_soup = soup(page_html, "html.parser")

   #grabs info for each textbook
   containers = page_soup.findAll("div",{"class":"LongDescription"})
   author = page_soup.select("p")

   for container in containers:
       item = {}
       item['type'] = "Textbook"
       item['title'] = container.find("div",{"class":"twothird"}).h1.text
       item['author'] = author[3].get_text(separator=', ')
       if item['author'] == " ":
          item['author'] = "University of Minnesota Libraries Publishing"
       item['link'] = "https://open.umn.edu/opentextbooks/BookDetail.aspx?bookId=" + str(i)
       item['source'] = "Open Textbook Library"
       item['base_url'] = "https://open.umn.edu/opentextbooks/"
       item['license'] = container.find("p",{"class":"Badge-Condition"}).a.text
       if item['license'] != container.find("p",{"class":"Badge-Condition"}).a.text:
          item['license'] = ""
       item['license_url'] = container.find("p",{"class":"Badge-Condition"}).a["href"]
       data.append(item) # add the item to the list

   with open("./json/noSubject/otl-loop.json", "w") as writeJSON:
      json.dump(data, writeJSON, ensure_ascii=False)

【问题讨论】：

标签： python python-3.x beautifulsoup

【解决方案1】：

我想通了。我的主要问题是item['license'] 这是我的解决方法：

if container.find("p",{"class":"Badge-Condition"}).a:
        item['license'] = container.find("p",{"class":"Badge-Condition"}).a.text
if container.find("img",{"class":"ctl00_maincontent_imgLicence"}):
        item['license'] = ''
if container.find("p",{"class":"Badge-Condition"}).a:
        item['license_url'] = container.find("p",{"class":"Badge-Condition"}).a["href"]
if container.find("img",{"class":"ctl00_maincontent_imgLicence"}):
        item['license_url'] = ''

【讨论】：