title: How to make this code execute faster?
body: <pre><code>def lookfor(alist, number):
    if number in alist:
      return alist.index(number)
    else:
      return "no"
  </code></pre>
  
  <p>So basically I input hundreds of thousands of numbers and I have to send each one of them thorugh "lookfor" to get an output of either the index of "number" in "alist" or get"no" if the number isn't there.
  It perfectly computes when I input not as many numbers but takes several minutes when I input xx,xxx-xxx,xxx numbers.
  Any suggestions? </p>