title: Python/Pandas - Writing empty cells to a csv file (instead of zeros)
body: <p>Running Python 3.8.1, 64 bit, on Windows 10.</p>
  
  <p>I have a csv file with two columns. The first column does not have numeric values on every row (=empty cells in between cells with values) and second has numeric values on every row.</p>
  
  <pre><code>column_1 column_2
           200
  13       201
           202
           203
           204
           205
  129      206
  16       207
           208
  </code></pre>
  
  <p>I read the csv file (shown above) with Pandas:</p>
  
  <pre><code>df = pd.read_csv("old.csv")
  </code></pre>
  
  <p>I make modifications to the Pandas dataframe and write to a new csv file with Pandas without the index column.</p>
  
  <pre><code>df.to_csv("new.csv", sep=',', encoding='utf-8', index=False)
  </code></pre>
  
  <p>The result is a csv file that has zeros in place of the original empty cells.</p>
  
  <pre><code>column_1,column_2
  0,200
  13,201
  0,202
  0,203
  0,204
  0,205
  129,206
  16,207
  0,208
  </code></pre>
  
  <p>My question: <strong>how to modify my script to write empty cells instead of zeros (0) in the csv file (i.e. the rows where column_2 value is 200, 202, 203, 204, 205 and 208)?</strong></p>