title: Python: Time of day to execute
body: <p>I have written a small script to fetch instant stock prices.</p>
  
  <pre><code>#script to get stock data
  
  from __future__ import print_function
  import urllib
  import lxml.html
  from datetime import datetime
  import sys
  import time
  
  stocks=["stock1","stock2","stock3","stock4","stock5"]
  
  while True:
   f=open('./out.txt', 'a+')
   for x in stock:
    url = "http://someurltofetchdata/"+x
    code   = urllib.urlopen(url).read()
    html   = lxml.html.fromstring(code)
    result = html.xpath('//td[@class="LastValue"][position() = 1]')
    result = [el.text_content() for el in result]
    f.write(datetime.now().strftime("%Y-%m-%d %H:%M:%S") + ' ' + x + ' ' + result[0])
    f.write("\n")
   f.close()
  </code></pre>
  
  <p>I want that code to fetch data only on hours the stock market is open which means on trading hours. (09:00 to 12:30 and 13:30 to 17:30).</p>
  
  <p>Could you please suggest a method to perform the scheduling implicitly on the code? (Not on the OS level)</p>