DOWNLOAD AF FILER FRA INTERNETTET VED HJÆLP AF PYTHON

Forespørgsler er et alsidigt HTTP-bibliotek i python med forskellige applikationer. Et af dets applikationer er at downloade en fil fra internettet ved hjælp af filens URL. Installation: First of all you would need to download the requests library. You can directly install it using pip by typing following command:

pip install requests

Or download it directly from her og installere manuelt.

Downloader filer

Python3

    # imported the requests library   import   requests   image_url   =   'https://www.python.org/static/community_logos/python-logo-master-v3-TM.webp'   # URL of the image to be downloaded is defined as image_url   r   =   requests  .  get  (  image_url  )   # create HTTP response object   # send a HTTP request to the server and save   # the HTTP response in a response object called r   with   open  (  'python_logo.webp'    'wb'  )   as   f  :   # Saving received content as a png file in   # binary format   # write the contents of the response (r.content)   # to a new file in binary mode.   f  .  write  (  r  .  content  )

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: 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 store filer

HTTP-svarets indhold ( r.indhold ) er intet andet end en streng, som gemmer fildataene. Så det vil ikke være muligt at gemme alle data i en enkelt streng i tilfælde af store filer. For at løse dette problem laver vi nogle ændringer i vores program:

Da alle fildata ikke kan gemmes af en enkelt streng, bruger vi r.iter_content metode til at indlæse data i bidder, der angiver chunk-størrelsen.

 r = requests.get(URL stream = True)

Setting strøm parameter til ægte vil kun forårsage download af svaroverskrifter, og forbindelsen forbliver åben. Dette undgår at læse indholdet på én gang i hukommelsen for store svar. En fast del vil blive indlæst hver gang mens r.iter_content is iterated. Here is an example: Python3

    import   requests   file_url   =   'http://codex.cs.yale.edu/avi/db-book/db4/slide-dir/ch1-2.pdf'   r   =   requests  .  get  (  file_url     stream   =   True  )   with   open  (  'python.pdf'    'wb'  )   as   pdf  :   for   chunk   in   r  .  iter_content  (  chunk_size  =  1024  ):   # writing one chunk at a time to pdf file   if   chunk  :   pdf  .  write  (  chunk  )

Downloader videoer

I dette eksempel er vi interesserede i at downloade alle de tilgængelige videoforelæsninger om dette webside . Alle arkiverne for dette foredrag er tilgængelige her . So we first scrape the webpage to extract all video links and then download the videos one by one. Python3

    import   requests   from   bs4   import   BeautifulSoup   '''    URL of the archive web-page which provides link to    all video lectures. It would have been tiring to    download each video manually.    In this example we first crawl the webpage to extract    all the links and then download videos.    '''   # specify the URL of the archive here    archive_url   =   'https://public.websites.umich.edu/errors/404.html   def   get_video_links  ():   # create response object    r   =   requests  .  get  (  archive_url  )   # create beautiful-soup object    soup   =   BeautifulSoup  (  r  .  content    'html5lib'  )   # find all links on web-page    links   =   soup  .  findAll  (  'a'  )   # filter the link sending with .mp4    video_links   =   [  archive_url   +   link  [  'href'  ]   for   link   in   links   if   link  [  'href'  ]  .  endswith  (  'mp4'  )]   return   video_links   def   download_video_series  (  video_links  ):   for   link   in   video_links  :      '''iterate through all links in video_links     and download them one by one'''   # obtain filename by splitting url and getting    # last string    file_name   =   link  .  split  (  '/'  )[  -  1  ]   print  (   'Downloading file:  %s  '  %  file_name  )   # create response object    r   =   requests  .  get  (  link     stream   =   True  )   # download started    with   open  (  file_name     'wb'  )   as   f  :   for   chunk   in   r  .  iter_content  (  chunk_size   =   1024  *  1024  ):   if   chunk  :   f  .  write  (  chunk  )   print  (   '  %s   downloaded!  n  '  %  file_name   )   print   (  'All videos downloaded!'  )   return   if   __name__   ==   '__main__'  :   # getting all video links    video_links   =   get_video_links  ()   # download all videos    download_video_series  (  video_links  )

Advantages of using Requests library to download web files are:

Man kan nemt downloade webmapperne ved at iterere rekursivt gennem hjemmesiden!
Dette er en browser-uafhængig metode og meget hurtigere!
Man kan simpelthen skrabe en webside for at få alle fil-URL'erne på en webside og dermed downloade alle filer i en enkelt kommando-
Implementering af Web Scraping i Python med BeautifulSoup

Denne blog er bidraget af Nikhil Kumar. Opret quiz