技术控

    今日:260| 主题:58206
收藏本版 (1)
最新软件应用技术尽在掌握

[其他] Downloading files from web using Python

[复制链接]
兜兜转转 投递于 2016-11-30 02:49:03
141 5
Requests is a versatile HTTP library in python with various applications. One of its applications is to download a file from web using the file URL.
   Installation:First of all, you would need to download the requests library. You can directly install it using pip by typing following command:
  1. pip install requests
复制代码
  Or download it directly from here and install manually.
  Downloading files

  1. # imported the requests library
  2. import requests
  3. image_url = "https://www.python.org/static/community_logos/python-logo-master-v3-TM.png"

  4. # URL of the image to be downloaded is defined as image_url
  5. r = requests.get(image_url) # create HTTP response object

  6. # send a HTTP request to the server and save
  7. # the HTTP response in a response object called r
  8. with open("python_logo.png",'wb') as f:

  9.     # Saving received content as a png file in
  10.     # binary format

  11.     # write the contents of the response (r.content)
  12.     # to a new file in binary mode.
  13.     f.write(r.content)
复制代码
    This small piece of code written above will download the following image from the web. Now check your local directory(the folder where this script resides), and you will find this image:
   

Downloading files from web using Python

Downloading files from web using Python-1-技术控-following,download,contents,directly,received
   All we need is the URL of the image source. (You can get the URL of image source by right-clicking on the image and selecting the View Image option.)
    Download large files

   The HTTP response content ( r.content ) is nothing but a string which is storing the file data. So, it won’t be possible to save all the data in a single string in case of large files. To overcome this problem, we do some changes to our program:
   Since all file data can’t be stored by a single string, we use r.iter_content method to load data in chunks, specifying the chunk size.
  1. r = requests.get(URL, stream = True)
复制代码
  Setting stream parameter to True will cause the download of response headers only and the connection remains open. This avoids reading the content all at once into memory for large responses. A fixed chunk will be loaded each time while r.iter_content is iterated.
  Here is an example:
  1. import requests
  2. file_url = "http://codex.cs.yale.edu/avi/db-book/db4/slide-dir/ch1-2.pdf"

  3. r = requests.get(file_url, stream = True)

  4. with open("python.pdf","wb") as pdf:
  5.     for chunk in r.iter_content(chunk_size=1024):

  6.          # writing one chunk at a time to pdf file
  7.          if chunk:
  8.              pdf.write(chunk)
复制代码
Downloading Videos

   In this example, we are interested in downloading all the video lectures available on this web-page . All the archives of this lecture are available here . So, we first scrape the webpage to extract all video links and then download the videos one by one.
  1. import requests
  2. from bs4 import BeautifulSoup

  3. '''
  4. URL of the archive web-page which provides link to
  5. all video lectures. It would have been tiring to
  6. download each video manually.
  7. In this example, we first crawl the webpage to extract
  8. all the links and then download videos.
  9. '''

  10. # specify the URL of the archive here
  11. archive_url = "http://www-personal.umich.edu/~csev/books/py4inf/media/"

  12. def get_video_links():
  13.    
  14.     # create response object
  15.     r = requests.get(archive_url)
  16.    
  17.     # create beautiful-soup object
  18.     soup = BeautifulSoup(r.content,'html5lib')
  19.    
  20.     # find all links on web-page
  21.     links = soup.findAll('a')

  22.     # filter the link sending with .mp4
  23.     video_links = [archive_url + link['href'] for link in links if link['href'].endswith('mp4')]

  24.     return video_links


  25. def download_video_series(video_links):

  26.     for link in video_links:

  27.         '''iterate through all links in video_links
  28.         and download them one by one'''
  29.         
  30.         # obtain filename by splitting url and getting
  31.         # last string
  32.         file_name = link.split('/')[-1]   

  33.         print "Downloading file:%s"%file_name
  34.         
  35.         # create response object
  36.         r = requests.get(link, stream = True)
  37.         
  38.         # download started
  39.         with open(file_name, 'wb') as f:
  40.             for chunk in r.iter_content(chunk_size = 1024*1024):
  41.                 if chunk:
  42.                     f.write(chunk)
  43.         
  44.         print "%s downloaded!\n"%file_name

  45.     print "All videos downloaded!"
  46.     return


  47. if __name__ == "__main__":

  48.     # getting all video links
  49.     video_links = get_video_links()

  50.     # download all videos
  51.     download_video_series(video_links)
复制代码
Advantages of using Requests library to download web files are:
  
       
  • One can easily download the web directories by iterating recursively through the website!   
  • This is a browser-independent method and much faster!   
  • One can simply scrape a web page to get all the file URLs on a webpage and hence, download all files in a single command-          Implementing Web Scraping in Python with BeautifulSoup
      
  This blog is contributed by Nikhil Kumar. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to [email protected] See your article appearing on the GeeksforGeeks main page and help other Geeks.
  Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



上一篇:Codebattles: Competitive Coding in the Workplace
下一篇:7 Time Series Datasets for Machine Learning
saikik 投递于 2016-11-30 08:23:54
再踩踩,楼主辛苦了!
回复 支持 反对

使用道具 举报

qn6r0qnm 投递于 2016-11-30 11:16:15
珍爱生命,{username}果断回帖。
回复 支持 反对

使用道具 举报

chen987long 投递于 2016-12-1 06:32:31
做人必备的100项技能,看帖回帖是一项!
回复 支持 反对

使用道具 举报

haix610 投递于 2016-12-7 22:25:14
顶!顶!顶!
回复 支持 反对

使用道具 举报

步步惊云 投递于 2016-12-7 23:39:24
学习下
回复 支持 反对

使用道具 举报

我要投稿

回页顶回复上一篇下一篇回列表
手机版/CoLaBug.com ( 粤ICP备05003221号 | 文网文[2010]257号 | 粤公网安备 44010402000842号 )

© 2001-2017 Comsenz Inc.

返回顶部 返回列表