title: Pandas - Counting quantity of commas in character field
body: <p>I have a pandas dataframe with a column filled with strings as is shown below:</p>
  
  <pre><code>   string_column
  0  t,d,t,d,v,d
  1  s,v,y,d
  2  d,u,f
  </code></pre>
  
  <p>I would like to create a new column with the count of commas in the string column. My intended outcome is below:</p>
  
  <pre><code>   string_column  comma_count
  0  t,d,t,d,v,d    5
  1  s,v,y,d        3
  2  d,u,f          2
  </code></pre>
  
  <p>Is there a string reading method to pandas that will accomplish this task?</p>
  
  <p>Thanks</p>