title: Change all the values in dataframe without affecting the index
body: <p>How can I replace all the values to 0, without affecting the index of the dataframe.</p>
  <p>Here's an example code:</p>
  <pre><code>df = pd.DataFrame({'A':np.random.randint(10, size= 10), 'B':np.random.randint(10, size= 10), 'C':np.random.randint(10, size= 10), 'D':np.random.randint(10, size= 10)})
  
     A  B  C  D
  0  6  5  3  8
  1  0  1  1  9
  2  9  3  0  7
  3  1  9  1  9
  4  3  5  7  5
  5  0  5  3  2
  6  8  8  7  9
  7  6  2  9  5
  8  5  8  8  0
  9  9  4  7  2
  </code></pre>
  <p>Is there a way to do it using lambda?</p>