LASTE NED FILER FRA NETTET VED HJELP AV PYTHON

Forespørsler er et allsidig HTTP-bibliotek i python med ulike applikasjoner. En av applikasjonene er å laste ned en fil fra nettet ved å bruke filens URL. Installasjon: 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.

Laster ned 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.)

Last ned store filer

HTTP-responsinnholdet ( r.innhold ) er ikke annet enn en streng som lagrer fildataene. Så det vil ikke være mulig å lagre alle dataene i en enkelt streng i tilfelle store filer. For å løse dette problemet gjør vi noen endringer i programmet vårt:

Siden alle fildata ikke kan lagres av en enkelt streng bruker vi r.iter_content metode for å laste data i biter som spesifiserer bitstørrelsen.

 r = requests.get(URL stream = True)

Setting strøm parameter til ekte vil kun føre til nedlasting av svarhoder og tilkoblingen forblir åpen. Dette unngår å lese innholdet på en gang i minnet for store svar. En fast del vil bli lastet inn 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  )

Laster ned videoer

I dette eksemplet er vi interessert i å laste ned alle videoforelesningene som er tilgjengelige om dette web-side . Alle arkivene til dette foredraget er tilgjengelige 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 enkelt laste ned nettkatalogene ved å iterere rekursivt gjennom nettsiden!
Dette er en nettleseruavhengig metode og mye raskere!
Man kan ganske enkelt skrape en nettside for å få alle fil-URLene på en nettside og dermed laste ned alle filene i en enkelt kommando-
Implementering av nettskraping i Python med BeautifulSoup

Denne bloggen er bidratt av Nikhil Kumar. Lag quiz