Scrape poll aggregators for current odds

election_odds.rb

#!/usr/bin/env ruby
require 'nokogiri'
require 'open-uri'

module OddsGetter
  class OddsGetter
    def initialize(url:, selector:, selector_type: :xpath, processing_func: ->(h) { h.text.to_f })
      @url = url
      @processing_func = processing_func
      @selector = selector
      @selector_type = selector_type
    end

    def odds
      processing_func.call(odds_string)
    end

    private

    attr_reader :url, :processing_func, :selector, :selector_type, :html

    def html
      @html ||= Nokogiri::HTML(open(url))
    end

    def odds_string
      selector_func = { css: :at_css, xpath: :at_xpath }.fetch(selector_type)
      html.public_send(selector_func, selector)
    end
    end

  site_data = {
    '538 Odds' => { url: 'http://projects.fivethirtyeight.com/2016-election-forecast/', selector: 'div.candidate.one.dem p.candidate-val.winprob', selector_type: :css },
    'Betting Market Odds' => { url: 'https://electionbettingodds.com/', selector: '//table//span[text()="Presidency"]/ancestor::table//img[@src="/Clinton.jpg"]/ancestor::tr//p[1]' },
    'Princeton Odds' => { url: 'http://election.princeton.edu/electoral-college-map/', selector: '//li[contains(text(), "Clinton Nov.")]', processing_func: -> (h) { h.text.match(/random drift.*?(\d+(\.\d)?)/)[1].to_f } }
  }

  puts "2016 Election Odds\n=================="
  padding = site_data.keys.map { |k| site_data.keys.map(&:length).max - k.length }
  site_data.each_with_index do |(site, site_data), i|
    puts "#{site}:#{' ' * padding[i]} #{OddsGetter.new(site_data).odds}"
  end
end