title: python - simple way to join 2 arrays/lists based on common values
body: <p>I have tried for a while but can't find a simple way to join 2 lists or arrays based only on common values. Similar to an SQL inner join but with arrays/lists and not dict, or some other data type. eg.</p>
  
  <pre><code>a = [1, 2, 3]
  b = [2, 3, 4]
  join(a, b)
  </code></pre>
  
  <p>prints</p>
  
  <pre><code>[2, 3]
  </code></pre>
  
  <p>seems so simple but lacking from python or numpy.</p>