title: Python Pandas concatenate strings and numbers into one string
body: <p>I am working with a pandas dataframe and trying to concatenate multiple string and numbers into one string. </p>
  
  <p>This works</p>
  
  <pre><code>df1 = pd.DataFrame({'Col1': ['a', 'b', 'c'], 'Col2': ['a', 'b', 'c']})
  df1.apply(lambda x: ', '.join(x), axis=1)
  
  0    a, a
  1    b, b
  2    c, c
  </code></pre>
  
  <p>How can I make this work just like df1?</p>
  
  <pre><code>df2 = pd.DataFrame({'Col1': ['a', 'b', 1], 'Col2': ['a', 'b', 1]})
  df2.apply(lambda x: ', '.join(x), axis=1)
  
  TypeError: ('sequence item 0: expected str instance, int found', 'occurred at index 2')
  </code></pre>