循环浏览多个页面时，如果页面上不存在元素，则跳过项目 - BeautifulSoup 和 Python

Question

我有一个脚本，可以循环浏览网站的多个页面，我想跳过或为可能不在某些页面上的项目添加空格。 例如，有些页面不包含许可证。 当我遇到其中一个页面时，我收到一个属性错误。 我下面的脚本可以毫无问题地循环浏览前两页，但是当它到达第三页时，它会停止。 我该如何解决这个问题？ 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)

Answer 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'] = ''