title: deleting useless columns and rows in csvfile and save using python
body: <p>Here's a sample csv file;</p>
  
  <pre><code>out_gate,uless_col,in_gate,n_con
  p,x,x,1
  p,x,y,1
  p,x,z,1
  a_a,u,b,1
  a_a,s,b,3
  a_b,e,a,2
  a_b,l,c,4
  a_c,e,a,5
  a_c,s,b,5
  a_c,s,b,3
  a_c,c,a,4
  a_d,o,c,2
  a_d,l,c,3
  a_d,m,b,2
  p,y,x,1
  p,y,y,1
  p,y,z,3
  </code></pre>
  
  <p>I want to remove the useless columns (2nd column) and useless rows (first three and last three rows) and create a new csv file and then save this new one. and How can I deal with the csv file that has more than 10 useless columns and useless rows?</p>
  
  <p>(assuming useless rows are located only on the top or the bottom lines not scattered in the middle)</p>
  
  <p>(and I am also assuming all the rows we want to use has its first element name starting with 'a_')</p>
  
  <p>Can I get solution without using numpys or pandas as well? thanks!</p>