title: How can I keep leading zeros in a column, when I export to CSV?
body: <p>I am trying to export a dataframe with a column with leading zeros like this: </p>
  
  <pre><code>df["CD_LIN_NEG"]
  
  0     001
  1     001
  2     004
  3     001
  4     001
  5     001
  6     003
  7     006
  Name: CD_LIN_NEG, dtype: object
  </code></pre>
  
  <p>But when I export to csv, all of the leading zeros are cut off any numbers when I open the file in Excel. How can I keep the zeros?</p>
  
  <p>I have tried to convert to string but it doesn't work:</p>
  
  <pre><code>df["CD_LIN_NEG"] = df['T_PROD_CP.LN'].astype(str).apply(lambda x: x.zfill(3))
  </code></pre>
  
  <p>or in this way:</p>
  
  <pre><code>df["CD_LIN_NEG"] = '00' + df['T_PROD_CP.LN'].astype(str)
  </code></pre>