title: IPython: run script starting from a specific line
body: <p>I am writing my script interactively with IPython. This is what I currently do: </p>
  
  <ol>
  <li>write a chunk of code,</li>
  <li>run in ipython with "run -i file_name.py". </li>
  <li>make changes and repeat 2 until I think it is OK .</li>
  <li>comment out the entire previous chunk.</li>
  <li>write new chunk of code that is based on the previous one.</li>
  <li>go back to step 2.</li>
  <li>......</li>
  </ol>
  
  <p>Is there more efficient way? Can I start a script from a specific line while using all the variables in current namespace?</p>