title: Python: how to keep leading zeros with dataframe.to_csv
body: <p>There is a dataframe (df1) like as following after I read the data from txt file:</p>
  
  <pre><code> name   l1     l2
    a    00000  00000 
    b    00010  00002
    c    00000  01218
  </code></pre>
  
  <p>When I use the python code as following:</p>
  
  <pre><code>dataframe.to_csv('test.csv', index= False)
  </code></pre>
  
  <p>Then I use the following code to read:</p>
  
  <pre><code>  df = pd.read_csv('test.csv')
  </code></pre>
  
  <p>I found the dataframe is being df2 as following </p>
  
  <pre><code>       name   l1      l2
          a      0       0
          b     10       2
          c      0      1218
  </code></pre>
  
  <p>But I want to keep the leading zero in the dataframe like df1.</p>
  
  <p>Thanks!</p>