title: Set a column in numpy array to zero
body: <p>I want to set a column in numpy array to zero at different times, in other words, I have numpy array <code>M</code> with size 5000x500. When I enter shape command the result is (5000,500), I think 5000 are rows and 500 are columns </p>
  
  <pre><code>shape(M)
  (5000,500)
  </code></pre>
  
  <p>But the problem when I want to access one column like first column</p>
  
  <pre><code>Mcol=M[:][0]
  </code></pre>
  
  <p>Then I check by shape again with new matrix <code>Mcol</code></p>
  
  <pre><code>shape(Mcol)
  (500,)
  </code></pre>
  
  <p>I expected the results will be (5000,) as the first has 5000 rows. Even when changed the operation the result was the same</p>
  
  <pre><code>shape(M)
  (5000,500)
  Mcol=M[0][:]
  shape(Mcol)
  (500,)
  </code></pre>
  
  <p>Any help please in explaining what happens in my code and if the following operation is right to set one column to zero</p>
  
  <pre><code>M[:][0]=0
  </code></pre>