title: sum for every row values through columns pandas
body: <p>This is my dataframe and I want to sum for every row values through columns A,B,C,D and append column 'Summ'</p>
  
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>A B C D Summ
  0 1 1 0 0 1+1+0+0
  1 0 0 1 1 0+0+1+1
  2 0 0 1 0 0+0+1+0
  3 1 1 1 1 1+1+1+1
  4 1 0 1 0 1+0+1+0</code></pre>
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