title: Easy Way to See if Two Columns are One-to-One in Pandas
body: <p>Working with data in Python 3+ with pandas. It seems like there should be an easy way to check if two columns have a one-to-one relationship (regardless of column type), but I'm struggling to think of the best way to do this.</p>
  
  <p>Example of expected output:</p>
  
  <pre><code>A    B     C
  0    'a'   'apple'
  1    'b'   'banana'
  2    'c'   'apple'
  </code></pre>
  
  <p>A &amp; B are one-to-one? TRUE</p>
  
  <p>A &amp; C are one-to-one? FALSE</p>
  
  <p>B &amp; C are one-to-one? FALSE</p>