Learning Python Networking - Second Edition

Downloading an RFC with urllib

Now, we are going to write our Python script using the urllib module. For this, create a text file called RFC_download_urllib.py:

#!/usr/bin/env python3import sys, urllib.requesttry:    rfc_number = int(sys.argv[1])except (IndexError, ValueError):    print('Must supply an RFC number as first argument')    sys.exit(2)template = 'http://www.rfc-editor.org/rfc/rfc{}.txt'url = template.format(rfc_number)rfc_raw = urllib.request.urlopen(url).read()rfc = rfc_raw.decode()print(rfc)

We can run the preceding code by using the following command:

$ python RFC_download_urllib.py 2324

This is the output of the previous script, where we can see the RFC description document:

First, we import our modules and check whether an RFC number ...