使用请求时未提供架构和其他错误。get（）

Question

我正在学习Python，学习的方法是将无聊的事情自动化。这个程序应该转到http://xkcd.com/并下载所有图像以供脱机查看。

我在2.7版和Mac上。

出于某种原因，我得到了一些错误，比如“没有提供模式”和使用request.get（）本身时的错误。

这是我的代码：

# Saves the XKCD comic page for offline read

import requests, os, bs4, shutil

url = 'http://xkcd.com/'

if os.path.isdir('xkcd') == True: # If xkcd folder already exists
    shutil.rmtree('xkcd') # delete it
else: # otherwise
    os.makedirs('xkcd') # Creates xkcd foulder.


while not url.endswith('#'): # If there are no more posts, it url will endswith #, exist while loop
    # Download the page
    print 'Downloading %s page...' % url
    res = requests.get(url) # Get the page
    res.raise_for_status() # Check for errors

    soup = bs4.BeautifulSoup(res.text) # Dowload the page
    # Find the URL of the comic image
    comicElem = soup.select('#comic img') # Any #comic img it finds will be saved as a list in comicElem
    if comicElem == []: # if the list is empty
        print 'Couldn\'t find the image!'
    else:
        comicUrl = comicElem[0].get('src') # Get the first index in comicElem (the image) and save to
        # comicUrl

        # Download the image
        print 'Downloading the %s image...' % (comicUrl)
        res = requests.get(comicUrl) # Get the image. Getting something will always use requests.get()
        res.raise_for_status() # Check for errors

        # Save image to ./xkcd
        imageFile = open(os.path.join('xkcd', os.path.basename(comicUrl)), 'wb')
        for chunk in res.iter_content(10000):
            imageFile.write(chunk)
        imageFile.close()
    # Get the Prev btn's URL
    prevLink = soup.select('a[rel="prev"]')[0]
    # The Previous button is first <a rel="prev" href="/1535/" accesskey="p">&lt; Prev</a>
    url = 'http://xkcd.com/' + prevLink.get('href')
    # adds /1535/ to http://xkcd.com/

print 'Done!'

以下是错误：

Traceback (most recent call last):
  File "/Users/XKCD.py", line 30, in <module>
    res = requests.get(comicUrl) # Get the image. Getting something will always use requests.get()
  File "/Library/Python/2.7/site-packages/requests/api.py", line 69, in get
    return request('get', url, params=params, **kwargs)
  File "/Library/Python/2.7/site-packages/requests/api.py", line 50, in request
    response = session.request(method=method, url=url, **kwargs)
  File "/Library/Python/2.7/site-packages/requests/sessions.py", line 451, in request
    prep = self.prepare_request(req)
  File "/Library/Python/2.7/site-packages/requests/sessions.py", line 382, in prepare_request
    hooks=merge_hooks(request.hooks, self.hooks),
  File "/Library/Python/2.7/site-packages/requests/models.py", line 304, in prepare
    self.prepare_url(url, params)
  File "/Library/Python/2.7/site-packages/requests/models.py", line 362, in prepare_url
    to_native_string(url, 'utf8')))
requests.exceptions.MissingSchema: Invalid URL '//imgs.xkcd.com/comics/the_martian.png': No schema supplied. Perhaps you meant http:////imgs.xkcd.com/comics/the_martian.png?

问题是我已经多次阅读了书中关于程序的部分，阅读了请求文档，以及这里的其他问题。我的语法看起来不错。

谢谢你的帮助！

编辑：

这不起作用：

comicUrl = ("http:"+comicElem[0].get('src')) 

我认为添加http:before可以消除无模式提供的错误。

Answer 1

说明：

一些XKCD页面有特殊的内容，而不是简单的图像文件。没关系，你可以跳过这些。如果选择器找不到任何元素，则soup.select（'35; comic img'）将返回一个空列表。

工作代码：

import requests,os,bs4,shutil

url='http://xkcd.com'

#making new folder
if os.path.isdir('xkcd') == True:
    shutil.rmtree('xkcd')
else:
    os.makedirs('xkcd')


#scrapiing information
while not url.endswith('#'):
    print('Downloading Page %s.....' %(url))
    res = requests.get(url)          #getting page
    res.raise_for_status()
    soup = bs4.BeautifulSoup(res.text)

    comicElem = soup.select('#comic img')     #getting img tag under  comic divison
    if comicElem == []:                        #if not found print error
        print('could not find comic image')

    else:
        try:
            comicUrl = 'http:' + comicElem[0].get('src')             #getting comic url and then downloading its image
            print('Downloading image %s.....' %(comicUrl))
            res = requests.get(comicUrl)
            res.raise_for_status()

        except requests.exceptions.MissingSchema:
        #skip if not a normal image file
            prev = soup.select('a[rel="prev"]')[0]
            url = 'http://xkcd.com' + prev.get('href')
            continue

        imageFile = open(os.path.join('xkcd',os.path.basename(comicUrl)),'wb')     #write  downloaded image to hard disk
        for chunk in res.iter_content(10000):
            imageFile.write(chunk)
        imageFile.close()

        #get previous link and update url
        prev = soup.select('a[rel="prev"]')[0]
        url = "http://xkcd.com" + prev.get('href')


print('Done...')