title: can I change value type in dataframe?
body: <p>can I change value type from string to float in dataframe</p>
  
  <p>for example df</p>
  
  <pre><code>    a      b
  0    0     0
  1    1     1 
  2    2     2
  </code></pre>
  
  <p>and df value type is string. </p>
  
  <pre><code>type (df['a'][0])  -&gt; str
  </code></pre>
  
  <p>is there a way to change all value type from string to float?
  should I use nested for loop? I tried to change as follows but it seems it's not the best way to change the type</p>
  
  <pre><code>for i in range(df(len)):
       df.loc['a',i] = float(df['a'][i])
       df.loc['b',i] = float(df['b'][i]) 
       i+=1..
  </code></pre>