Get the URL of the HTTP redirect destination in Python

Overview

--Get the URL of the HTTP redirect destination in Python 3 --Operation check environment: Python 3.8.5 + macOS Catalina

Source code

Save the following contents with the file name get_redirect.py.

get_redirect.py

import sys
import urllib.request

#Handler class that does not redirect
class NoRedirectHandler(urllib.request.HTTPRedirectHandler):
  # HTTPRedirectHandler.redirect_Override request
  def redirect_request(self, req, fp, code, msg, hdrs, newurl):
    self.newurl = newurl #Hold redirect URL
    return None

#Function to get the redirect URL
def get_redirect_url(src_url):
  #Set handlers that do not redirect
  no_redirect_handler = NoRedirectHandler()
  opener = urllib.request.build_opener(no_redirect_handler)
  try:
    with opener.open(src_url) as res:
      return None #It was a URL that didn't redirect
  except urllib.error.HTTPError as e:
    if hasattr(no_redirect_handler, "newurl"):
      return no_redirect_handler.newurl #Returns the redirect URL
    else:
      raise e #Rethrow because it is an exception that occurred other than the redirect

#Get command line arguments
src_url = sys.argv[1]

#Get the redirect URL
redirect_url = get_redirect_url(src_url)

#Output redirect URL
if redirect_url is not None:
  print(redirect_url)

Execution example.

$ python get_redirect.py https://bit.ly/3kmTOkc
https://t.co/yITSBp4ino

$ python get_redirect.py https://t.co/yITSBp4ino
https://qiita.com/niwasawa

$ python get_redirect.py https://qiita.com/niwasawa

Simplified version

Save the following contents with the file name get_redirect.py.

get_redirect.py

import sys
import urllib.request

#Function to get the redirect URL
def get_redirect_url(src_url):
  with urllib.request.urlopen(src_url) as res:
    url = res.geturl() #Get the final URL
    if src_url == url:
      return None #Not redirected because it is the same as the specified URL
    else:
      return url #Redirecting because it is different from the specified URL

#Get command line arguments
src_url = sys.argv[1]

#Get the redirect URL
redirect_url = get_redirect_url(src_url)

#Output redirect URL
if redirect_url is not None:
  print(redirect_url)

Execution example. In the simplified version, a request is sent to the redirect destination URL, and in the case of multi-stage redirect, the final URL is output.

$ python get_redirect.py https://bit.ly/3kmTOkc
https://qiita.com/niwasawa

$ python get_redirect.py https://t.co/yITSBp4ino
https://qiita.com/niwasawa

$ python get_redirect.py https://qiita.com/niwasawa

Reference material

-[urllib \ .request ---extensible library for opening URLs — Python 3 \ .8 \ .5 documentation](https://docs.python.org/ja/3.8/library/urllib .request.html) --How to get resources on the internet using the urllib package — Python 3 \ .8 \ .5 documentation -HTTP Redirection -HTTP \ | MDN

• Location - HTTP | MDN