title: Values changed after converting object type column to string column type Python
body: <p>I have two columns in my pandas dataframe</p>
  <pre><code>Current selling price      New selling price
    0.0374                         0.03927
    0.1154                         0.12117
    0.0424                         0.04452
    0.1154                         0.12117
    0.1062                         0.11151
    0.035                          0.03675
  </code></pre>
  <p>Both the column are of type object.  To do some analysis I want to convert them to string type so I used the below code.</p>
  <pre><code>df['Current selling price'] = df['Current selling price'].astype('string')
  df['New selling price'] = df['New selling price'].astype('string')
  </code></pre>
  <p>After conversion some of the values in the column changed with long decimal values.</p>
  <pre><code> Current selling price           New selling price
     0.0374                        0.039270000000000006
     0.1154                        0.12117000000000001    
     0.0424                        0.044520000000000004
     0.1154                        0.12117000000000001
     0.1062                        0.11151000000000001
     0.035                         0.036750000000000005  
  </code></pre>
  <p>Can anyone help me to solve this issue.</p>