def runUser():
       x = raw_input("Enter your username:")
       y = raw_input("Enter your password :")
       users = [x == "aeduun" and y == "1234", x == "paul" and y == "fifty"]
       raw_input("")
       if x == users[] and y == users[]:#x == "aeduun" and y == "1234":
           print "you are now logged in"
       elif x == "Mercuryisle" and y == "shrek":
           print "Your account has expired..."
                 "You will now bw taken back to the login page"
           time.sleep(5)
       return runUser()

users = set([("aeduun","1234"), ("paul","fifty")])
expired_users = set([("Mercuryisle", "shrek")])
. . .
if (x,y) in users:
    print "you are now logged in
elif (x,y) in expired_users:
    print "Your account has expired..."
. . .

def runUser():
   x = raw_input("Enter your username: ")
   y = raw_input("Enter your password: ")
   users = {"aeduun":"1234", "paul":"fifty"}
   raw_input("")
   if x in users:
       if y == users[x]:
           print "you are now logged in"
   elif x == "Mercuryisle" and y == "shrek":
       print "Your account has expired..."
             "You will now bw taken back to the login page"
       time.sleep(5)
   return runUser()

>>> runUser()
Enter your username: aeduun
Enter your password: 1234

you are now logged in
Enter your username: Mercuryisle
Enter your password: shrek

Your account has expired...You will now bw taken back to the login page
Enter your username: