you have to use it with cmd (terminal in mac and linux)

1. put it in same directory first (cd C:\users\name...)
2. then type in: python [name.py] ... You have 2 choices for --type parameter When parameters are less than needed or input is wrong it will give an error message And you can change file name for writing less (ex. creditc.py) (> python creditc.py ...) 1) > python Project3 - Credit Calculator.py --type=diff --principal=1000000 --periods=10 --interest=10 #calculate differentiated payments 2) > python Project3 - Credit Calculator.py --type=annuity --principal=1000000 --periods=60 --interest=10 #calculate annuity payment 3) > python Project3 - Credit Calculator.py --type=annuity --payment=8722 --periods=120 --interest=5.6 #calculate principal 4) > python Project3 - Credit Calculator.py --type=annuity --principal=500000 --payment=23000 --interest=7.8 #calculate months(years) needed

NOTE that when inputting --interest consider it as percentage (but it should be less or equal 12%), but without "%" sign. The program will understand that you typed it like percentage