title: Randomly generate 4 or 5 digit Unique Codes in Subsequent Runs of the Script
body: <p>I have a requirement to Generate 10 4 or 5 Digit unique numbers. 
  I can do that using Python/Perl, but the same script is going to run everyday to generate 10 random numbers. 
  So I don't want them to repeat. If I generate them randomly then there is a probability that they will repeat.</p>
  
  <p>Please suggest.</p>