title: Getting "Performance Warning" when trying to add multiple columns in pandas DataFrame
body: <p>Please find below a dataframe:</p>
  <p><a href="https://i.stack.imgur.com/UeLR2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UeLR2.png" alt="enter image description here" /></a></p>
  <p>Logic:
  For every new entry, first I need to check time if it exists. If it exists, I want to add new column suppose 'vlan3' with some value at the same index ('time') row.
  If there is no such time present, a new row with another time needs to be added.</p>
  <p>I have written a code trying to add multiple columns.</p>
  <p><a href="https://i.stack.imgur.com/5ad8c.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5ad8c.png" alt="enter image description here" /></a></p>
  <p>In this code, I am getting an error as below:</p>
  <p><a href="https://i.stack.imgur.com/jWOHK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jWOHK.png" alt="enter image description here" /></a></p>
  <p>Please advise how to add multiple columns satisfying the above mentioned logic.</p>