title: How to apply an expression on pandas dataframe
body: <p>I gets the expression and new column name as parameters.</p>
  <pre><code>aggExpression = &quot;(billDate.replace(day=1) + datetime.timedelta(days=32)).replace(day=1)&quot;
  comNewColName = &quot;nextMonthFirstOfBillDate&quot;
  </code></pre>
  <p>This is just calculate next month first date of billDate.</p>
  <pre><code>df = df.assign(comNewColName=lambda x: (pd.to_datetime(x['billDate']).replace(day=1) + datetime.timedelta(days=32)).replace(day=1)))
  </code></pre>
  <p>What I am trying to do: next month first date of billDate and rename the column as &quot;nextMonthFirstOfBillDate&quot;.</p>