title: Get DataFrame of indexed value of value indexed of from a DF for the whole column
body: <p>I have a Pandas DataFrame:</p>
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; df
          a       b        c
  foo  john  george  micheal
  bar  sean   david      sam
  </code></pre>
  <p>Now I want a DataFrame which has only first two characters of all columns by processing the above.
  So after some statement, <code>df</code> should become:</p>
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; df
          a    b     c
  foo     jo   ge    mi
  bar     se   da    sa
  </code></pre>
  <p>I have tried options like : <code>df['a'].str[:2]</code>, this works but it only satisfies for one column, if I try for multiple columns like <code>df[df.columns].str[:2]</code> or <code>df[:].str[:2]</code> It throws error.
  So how can I achieve that?</p>