退出无限循环

Question

我已经编写了下载图像的程序，用于形成soup.io.

from bs4 import BeautifulSoup as soup 
import urllib.request 
import requests 
import os.path 

login = "test-site" #input('Enter soup login:') 
website = "http://" + login + ".soup.io" 
path = 'images' 

if not os.path.exists(path): 
    os.makedirs(path) 

openWebsite = soup(urllib.request.urlopen(website), 'html.parser') 
imageLink = openWebsite.find_all(name="div", attrs={'class': 'imagecontainer'}) 

i = 1 
for src in imageLink: 
    temp = src.find('img')['src'] 
    img_data = requests.get(temp).content 
    if temp.find('.gif') != -1: 
     filename = os.path.join(path, str(i) + '.gif') 
     with open(filename, 'wb') as handler: 
      handler.write(img_data) 
     i += 1 
    elif temp.find('.jpeg') != -1: 
     filename = os.path.join(path, str(i) + '.jpeg') 
     with open(filename, 'wb') as handler: 
      handler.write(img_data) 
     i += 1 
    else: 
     filename = os.path.join(path, str(i) + '.png') 
     with open(filename, 'wb') as handler: 
      handler.write(img_data) 
     i += 1 

nextPage = openWebsite.find_all(name="a", attrs={'class': 'more keephash'}) 

while str(nextPage): 
    for item in nextPage: 
     nextPageLink = website+item['href'] 

     for j in nextPageLink: 
      openWebsite = soup(urllib.request.urlopen(nextPageLink), "html.parser") 
      imageLink = openWebsite.find_all(name="div", attrs={'class': 'imagecontainer'}) 
      nextPage = openWebsite.find_all(name="a", attrs={'class': 'more keephash'}) 

      for g in nextPage: 
       nextPageLink = website + g['href'] 

      for src in imageLink: 
       temp = src.find('img')['src'] 
       img_data = requests.get(temp).content 
       if temp.find('.gif') != -1: 
        filename = os.path.join(path, str(i) + '.gif') 
        with open(filename, 'wb') as handler: 
         handler.write(img_data) 
        i += 1 
       elif temp.find('.jpeg') != -1: 
        filename = os.path.join(path, str(i) + '.jpeg') 
        with open(filename, 'wb') as handler: 
         handler.write(img_data) 
        i += 1 
       else: 
        filename = os.path.join(path, str(i) + '.png') 
        with open(filename, 'wb') as handler: 
         handler.write(img_data) 
        i += 1 

在每个页面上显示20个图像。在每个页面上，我都会抓取“更多”链接到较旧的页面（nextPageLink），并在每个图像保存在循环中后打开它。我的问题是我的程序在最后一页上循环（Where is no“More”链接），并从那里反复下载图像。我试图将nextPageLink分配给一个名为previousPage的新变量，然后使用if语句对其进行比较 - 如果链接相同，我想设置nextPage = False，但它不起作用 - nextPageLink不再更新，因为那里在网站上没有链接，所以我无法正确比较它。

Answer 1

作为@Marc B建议，我的问题是，我没有检查nextPage是否为空。所以解决方案很简单：

if openWebsite.find_all(name="a", attrs={'class': 'more keephash'}) == []: 
    break