Friendly ID / Auto Generate Invoice ID on First Save.
This is just modified version of friendly id for make this script compatible with python 3.x
Invoice numbers like "0000004" are a little unprofessional in that they expose how many sales a system has made, and can be used to monitor the rate of sales over a given time. They are also harder for customers to read back to you, especially if they are 10 digits long.
This is simply a perfect hash function to convert an integer (from eg an ID AutoField) to a unique number. The ID is then made shorter and more user-friendly by converting to a string of letters and numbers that wont be confused for one another (in speech or text).
To use it: