title: keep the same type and index structure after saving a dataframe in a csv
body: <p>I have a data frame like that</p>
  <pre><code>  Date            Cov_list
  0 01/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  0 01/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  1 02/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  1 02/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  </code></pre>
  <p>When saving this data frame to CSV file , I lose the data type of <code>Cov_list</code> column and it becomes a str , plus I lose the index numbers and instead I get this</p>
  <pre><code>  Unnamed: 0 Date            Cov_list
  0     0       01/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  1     0       01/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  2     1       02/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  3     1       02/01/2022     [[4.04 , 30.04 , 34.95],[33.3,2.33,54.5]]
  </code></pre>
  <p>I tried solving the Cov_list data type column using this , but it didn't work</p>
  <pre><code>data['cov_list'] = data['cov_list'].str.split(' ').apply(lambda x: [float(num) for num in x])
  </code></pre>
  <p>I got this error</p>
  <blockquote>
  <p>ValueError: could not convert string to float: '[[0.0004'</p>
  </blockquote>