title: Python Pandas VLookup with multiple columns equivalent
body: <p>I have some simulation results that I wish to pair with some static information I hold for their particular coordinates. </p>
  
  <p>I am using pandas and the <code>key</code> dataframe looks like this:</p>
  
  <pre><code>Orig_lat    Orig_lng    Dest_lat    Dest_lng    Site    Lane_1
  51.4410925  -0.0913334  51.4431736  -0.0681643  6   E
  51.4431736  -0.0681643  51.4410925  -0.0913334  6   W
  51.6300955  -0.0781079  51.6489284  -0.0602954  7   N
  51.648917   -0.0600521  51.6299841  -0.0779832  7   S
  51.4648078  -0.301316   51.4573656  -0.3219232  9   S
  51.4573656  -0.3219232  51.4649063  -0.3013827  9   N
  51.412392   0.0743042   51.4088694  0.0800096   11  S
  51.4088694  0.0800096   51.412392   0.0743042   11  N
  51.4728599  -0.0235216  51.4804927  -0.0231821  14  N
  </code></pre>
  
  <p>The results <code>dataframe</code> looks like this:</p>
  
  <pre><code>distance    duration    duration_in_traffic Orig_lat    Orig_lng    Dest_lat    Dest_lng    
  1456736402  1670    186 337 51.4431736  -0.0681643  51.4410925  -0.0913334
  1456736416  508 73  73  51.4380877  -0.2131928  51.4417083  -0.2168077
  1456736416  508 71  71  51.4417083  -0.2168077  51.4380877  -0.2131928
  1456736417  578 83  82  51.5229177  -0.4402988  51.5180086  -0.4391647
  1456736417  578 79  79  51.5180086  -0.4391647  51.5229177  -0.4402988
  1456736417  894 148 155 51.489123   -0.3015009  51.4886771  -0.2894982
  1456736418  894 170 163 51.4886771  -0.2894982  51.489123   -0.3015009
  1456736418  410 88  88  51.5294107  0.107865    51.5296292  0.1019929
  1456736418  410 91  90  51.5296292  0.1019929   51.5294107  0.107865
  1456736419  821 90  102 51.6043935  -0.340337   51.6038698  -0.3521945
  1456736419  821 96  121 51.6038698  -0.3521945  51.6043935  -0.340337
  1456736419  263 48  47  51.3718957  -0.0471616  51.3741868  -0.0480754
  1456736420  263 48  48  51.3741868  -0.0480754  51.3718957  -0.0471616
  1456736421  426 59  58  51.5122705  -0.2177689  51.5086821  -0.2156843
  1456736421  426 55  70  51.5086821  -0.2156843  51.5122705  -0.2177689
  1456736421  471 57  57  51.3782746  -0.1864154  51.3800551  -0.1916053
  </code></pre>
  
  <p>I wish to harvest the <code>Site</code> and <code>Lane_1</code> columns from the key and join these to the <code>results</code> dataframe using <code>Orig_lat</code>, <code>Orig_lng</code>, <code>Dest_lat</code>, <code>Dest_lng</code>, giving:</p>
  
  <pre><code>distance    duration    duration_in_traffic Orig_lat    Orig_lng    Dest_lat    Dest_lng, Site, Lane_1    
      1456736402  1670    186 337 51.4431736  -0.0681643  51.4410925  -0.0913334
      1456736416  508 73  73  51.4380877  -0.2131928  51.4417083  -0.2168077  41  N
      1456736416  508 71  71  51.4417083  -0.2168077  51.4380877  -0.2131928  41  S
      1456736417  578 83  82  51.5229177  -0.4402988  51.5180086  -0.4391647  42  S
      1456736417  578 79  79  51.5180086  -0.4391647  51.5229177  -0.4402988  42  N
      1456736417  894 148 155 51.489123   -0.3015009  51.4886771  -0.2894982  43  E
      1456736418  894 170 163 51.4886771  -0.2894982  51.489123   -0.3015009  43  W
      1456736418  410 88  88  51.5294107  0.107865    51.5296292  0.1019929   45  W
      1456736418  410 91  90  51.5296292  0.1019929   51.5294107  0.107865    45  E
      1456736419  821 90  102 51.6043935  -0.340337   51.6038698  -0.3521945  46  W
      1456736419  821 96  121 51.6038698  -0.3521945  51.6043935  -0.340337   46  E
      1456736419  263 48  47  51.3718957  -0.0471616  51.3741868  -0.0480754  48  N
      1456736420  263 48  48  51.3741868  -0.0480754  51.3718957  -0.0471616  48  S
      1456736421  426 59  58  51.5122705  -0.2177689  51.5086821  -0.2156843  54  S
      1456736421  426 55  70  51.5086821  -0.2156843  51.5122705  -0.2177689  54  N
      1456736421  471 57  57  51.3782746  -0.1864154  51.3800551  -0.1916053  58  W
  </code></pre>
  
  <p>How would I use merge to achieve this?</p>