title: extract month from date in python
body: <p>I have a column of dates in the format 2010-01-31. I can extract the year using</p>
  
  <pre><code>#extracting year
  year = df["date"].values
  year = [my_str.split("-")[0] for my_str in year]
  df["year"] = year
  </code></pre>
  
  <p>I'm trying to get the month, but I don't understand how to get it on the second split. </p>