This file has five python modules:
1.assignment8.py: when call python assignment8.py, the whole program will be called.
2.ExceptionClass.py: define two kinds of error when converting the token into int list.
3.input_object: class of defining a int list from the string of input
4.test.py:unittest for common error when asking for user for input (others are random methods which have indefinite result
5.methods.py: get the simulation result of the desired lists of positions and pos-values