title: delete every nth row or column in a matrix using Python
body: <p>I am trying to delete every 8th column in a 1024x1024 matrix using this <a href="https://stackoverflow.com/questions/3877491/deleting-rows-in-numpy-array">method</a> but it takes a lot of time and it will be more difficult when I have to process millions of matrices. Could you please show me how can I delete every nth row or column starting from a certain row or column and using numpy, scipy or any other Python package?</p>
  
  <p>Many thanks</p>