According to an article in Linux Journal #144, Reuven M. Lerner demonstrated how to extend web services using other web services in Ruby. This article is very interesting and I love it so much even it is Ruby. I don’t have much experience in Ruby so I wonder how it could be implemented in Python. That’s the point drived me to post this blog. The original article shown 3 short programs which query prices by given ISBN from Skokie Public Library and . The first one is just very simple and short program for searching ISBN in Skokie.

1. Script specification
   Ruby

   #!/usr/bin/ruby

   Python

   #!/usr/bin/python

2. Import statement
   Ruby

   require ’net/http’

   Python

   import sys
   import re
   import urllib

3. Validate argument
   Ruby

   if ARGV.length == 0
     puts "#{$0}: You must enter at least one argument"
     exit
   end

   Python

   if len(sys.argv) == 1:
       print "%s: You must enter at least one argument." % sys.argv[0]
       sys.exit()

4. Initialize output and regular expressions
   Ruby

   output = ""
    
   not_in_collection_re = /class="yourEntryWouldBeHereData"/ix
   on_shelf_re = /CHECK SHELF/ix
   checked_out_re = /DUE /ix

   Python

   output = ’’
    
   not_in_collection_re = re.compile(r’class="yourEntryWouldBeHereData"’,re.I)
   on_shelf_re = re.compile(r’CHECK SHELF’,re.I)
   checked_out_re = re.compile(r’DUE ’,re.I)

5. Start main loop
   Ruby

   ARGV.each do |isbn|

   Python

   for isbn in sys.argv[1:]:

6. Validate input
   Ruby

     if not isbn.match(/[0-9xX]{10}/)
       output << "ISBN #{isbn} is invalid.\n"
       next
     end

   Python

       if not re.match(r’[0-9xX]{10}’,isbn):
           output += ’ISBN %s is invalid.\n’ % isbn
           continue

7. Get query result
   Ruby

     response = Net::HTTP.get_response(’catalog.skokielibrary.info’,
                                       "/search~S4/i?SEARCH=#{isbn}")

   Python

       response = urllib.urlopen(’http://catalog.skokielibrary.info/search~S4/i’,
                                 ’SEARCH=%s’ % isbn)
       body = response.read()

8. Check result
   Ruby

     if not_in_collection_re.match(response.body)
       output << "ISBN #{isbn} is not in the Skokie collection.\n"
     elsif on_shelf_re.match(response.body)
       output << "ISBN #{isbn} is on the shelf.\n"
     elsif checked_out_re.match(response.body)
       output << "ISBN #{isbn} is currently checked out.\n"
     else
       output << "ISBN #{isbn} response: Unparseable!.\n"
     end

   Python

       if not_in_collection_re.search(body):
           output += ’ISBN %s is not in the Skokie collection.\n’
       elif on_shelf_re.search(body):
           output += ’ISBN %s is on the shelf.\n’
       elif checked_out_re.search(body):
           output += ’ISBN %s is currently checked out.\n’
       else:
           output += ’ISBN %s response: Unparseable!\n’

9. End main loop
   Ruby

   end

10. Show output
    Ruby

    puts output

    Python

    print output

I hope you are able to understand how Ruby and Python work for the same functions. Ruby seems to provide highly convenience string substitution while Python has very clean and clear syntax. Anyone could read Python code at a glance and understand its logic without Python knowledge.

Don't forget to read part 1, 2, 3.

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