title: Counting unique values in a column in pandas dataframe like in Qlik?
body: <p>If I have a table like this:  </p>
  
  <pre><code>df = pd.DataFrame({
           'hID': [101, 102, 103, 101, 102, 104, 105, 101],
           'dID': [10, 11, 12, 10, 11, 10, 12, 10],
           'uID': ['James', 'Henry', 'Abe', 'James', 'Henry', 'Brian', 'Claude', 'James'],
           'mID': ['A', 'B', 'A', 'B', 'A', 'A', 'A', 'C']
  })
  </code></pre>
  
  <p>I can do <code>count(distinct hID)</code> in Qlik to come up with count of 5 for unique hID.  How do I do that in python using a pandas dataframe?  Or maybe a numpy array?  Similarly, if were to do <code>count(hID)</code> I will get 8 in Qlik.  What is the equivalent way to do it in pandas?</p>