How can you make it simpler?

[DreamingInsanity]

x is the first digit

num2= 2nd digit
num3= 3rd digit
num4= 4th digit

With a little change, it works with this:

def fourdigit(first):
  n = random.randint(100, 999)
  n = str(first) + str(n)
  digits = set(n)
  if(len(digits) < len(n)):
    return fourdigit(first) 
  return int(n)

rather than generating a 4 digit number it just generates a 3 digit number and adds the first digit to the front.