title: Tell Python to wait/pause a 'for' loop
body: <p>I have a Python program that navigates me to a website with a function that I have defined as nav(a, b), and on this site I will be downloading some pyfits data for use on another script. This site has a different pyfits file for every set of (a,b) in a catalog I have.</p>
  <p>I was wondering if I could iterate through this catalog using a <code>for</code> loop, and each time the nav(a, b) function is used, tell python to pause while I download the file, then resume again when I tell it to. I've done something like this in <a href="https://en.wikipedia.org/wiki/IDL_%28programming_language%29" rel="noreferrer">IDL</a> before, but don’t know how with Python.</p>
  <p>Otherwise I guess I'm stuck running the program 200 times, replacing the (a, b) values each time, which will take for ever.</p>