title: Convert multiple columns to string in pandas dataframe
body: <p>I have a pandas data frame with different data types. I want to convert more than one column in the data frame to string type. I have individually done for each column but want to know if there is an efficient way?</p>
  
  <p>So at present I am doing something like this:</p>
  
  <pre><code>repair['SCENARIO']=repair['SCENARIO'].astype(str)
  
  repair['SERVICE_TYPE']= repair['SERVICE_TYPE'].astype(str)
  </code></pre>
  
  <p>I want a function that would help me pass multiple columns and convert them to strings.</p>