4J

This is perhaps more a note to self, but of course others are welcome to use and improve on the function.

#!/usr/bin/python

import traceback
import re

def UserInput( question="> ", input_type="numeric", regex="^\d{1}$", action_on_fail="retry", help_on_error="\tYou need to supply exactly 1 numeric digit from 0 to 9. Press CTRL+C to quit." ):
 quit  = 0
 userinput = ""
 while quit == 0:
  try:
   if input_type == "numeric":
    userinput = str( input( str( question ) ) ) 
   else:
    userinput = str( raw_input( str( question ) ) )
  except:
   print "ERROR - Exception: "
   print traceback.format_exc() 
  # Validate the input
  if re.compile( regex ).search( userinput ):
   quit = 1
  else:
   print "ERROR - Input validation failed."
   print str( help_on_error )
   if action_on_fail != "retry":
    userinput = ""
    quit = 1
   else:
    print ""
 return userinput

print "Testing user input...\n\n"
born = UserInput( "In which year were you born? ", "numeric", "^\d{4}$", "retry", "Enter a year valid 4 digit year" )
name = UserInput( "What is your name? ", "alpha", "^\w{3,32}$", "retry", "A valid name contains only alpha characters and is between 3 and 32 characters long" )
if int( born ) < 1980:
 print "Hi " + str( name ) + " - You are old :-)"
else:
 print str( name ) + " - you're a youngster..."

As you can see, I have used normal regex validation, so nothing too fancy.