Compute shared followers between two Twitter accounts

shared_followers.rb

#!/usr/bin/env ruby

# Author: Damon Clinkscales

require 'rubygems'
require 'hpricot'
require 'net/http'
require 'yaml'

def get_followers(user)  
  xml,url = "",""
  result = []

  http = Net::HTTP.new('twitter.com', 80)
  
  http.start do |http|
    url = "/followers/ids/#{user}.xml"
    req = Net::HTTP::Get.new(url)
    req.basic_auth(CONFIG["USERNAME"], CONFIG["PASSWORD"])
    response = http.request(req)
    xml = response.body
    doc = Hpricot(xml)
    followers = doc.search("//id")
    followers.each do |id|
      result << id.inner_text    
    end
  end
  result.uniq
end

def shared_followers(user1,user2)
  puts "Computing shared follower % between #{user1} and #{user2}...\n"

  user1_followers = get_followers(user1)
  user2_followers = get_followers(user2)

    
  puts "#{user1} has #{user1_followers.size} followers."
  puts "#{user2} has #{user2_followers.size} followers."
  shared_followers = (user1_followers & user2_followers)
  
  puts "They share #{shared_followers.size} followers."
  puts "#{sprintf("%.2f", (shared_followers.size / user1_followers.size.to_f*100).to_s)}% of #{user1}"
  puts "#{sprintf("%.2f", (shared_followers.size / user2_followers.size.to_f*100).to_s)}% of #{user2}"
end

####################################################################
## shared_followers test                                          ##
####################################################################
CONFIG = YAML::load(IO.read(File.dirname(__FILE__) + '/config.yml'))

if (ARGV[0] && ARGV[1])
  user1 = ARGV[0]
  user2 = ARGV[1]
else
  user1 = "jasonfried"
  user2 = "37signals"
end
  
shared_followers(user1,user2)

####################################################################
## example run                                                    ##
####################################################################
# $ shared_followers.rb 
# Computing shared follower % between jasonfried and 37signals...
# jasonfried has 6104 followers.
# 37signals has 10308 followers.
# They share 2804 followers.
# 45.94% of jasonfried
# 27.20% of 37signals