title: How to efficiently remove leading rows containing only 0 as value?
body: <p>I have a pandas dataframe and the first rows have only zeros as value.
  I would like to remove those rows.</p>
  
  <p>So, denoting df my dataframe and ['a', 'b', 'c'] its columns. I tried the following code.</p>
  
  <pre><code>df[(df[['a', 'b', 'c']] != 0).all(axis=1)]
  </code></pre>
  
  <p>But it will also turn the following dataframe :</p>
  
  <pre><code>a b c
  0 0 0
  0 0 0
  1 0 0
  0 0 0
  2 3 5
  4 5 6
  0 0 0
  1 1 1 
  </code></pre>
  
  <p>Into this one :</p>
  
  <pre><code>a b c
  1 0 0
  2 3 5
  4 5 6
  1 1 1
  </code></pre>
  
  <p>That's not what I want. I just want to focus on leading rows. So, I would like to have :</p>
  
  <pre><code>a b c
  1 0 0
  0 0 0
  2 3 5
  4 5 6 
  0 0 0
  1 1 1
  </code></pre>
  
  <p>It would be great to have a simple and efficient solution using pandas functions. Thanks</p>