Simple Reactive programming.

cell.py

from types import FunctionType

class cell:
    def __init__(self, *args):
        self.i_depend_on = []
        self.depends_on_me = []
        self.set(*args)

    def get(self):
        return self.value

    def add(self, depends):
        self.depends_on_me.append(depends)

    def remove(self, depends):
        self.depends_on_me.remove(depends)

    def set(self, *args):
        for depend in self.i_depend_on:
            depend.remove(self)

        if (len(args) == 0 or
            (len(args) > 1 and not isinstance(args[0], FunctionType))):
            raise TypeError("A Cell must have a value, OR a function and cell args.")

        if type(args[0]) == FunctionType:
            self.__class__ = cell_formula
            self.calculation = args[0]
            self.i_depend_on = list(args[1:])
            self.calc()
            for depend in self.i_depend_on:
                depend.add(self)
        else:
            self.__class__ = cell_value
            self.value = args[0]
            self.calculation = None

        for depends in self.depends_on_me:
            depends.calc()

class cell_value(cell):
    def calc(self): pass

class cell_formula(cell):
    def calc(self):
        self.value = self.calculation(*[depends.value for depends in self.i_depend_on])
        for depends in self.depends_on_me:
            depends.calc()

Reactive Programming