Symbolická matematika v Pythonu

sym_in_py.py

class Expression(object):
    def __add__(self, rt):
        return Plus(self, rt)
    def __sub__(self, rt):
        return Minus(self, rt)
    def __mul__(self, rt):
        return Multiply(self, rt)
    def __div__(self, rt):
        return Divide(self, rt)

class BinaryOperation(Expression):
    def __init__(self, lt, rt):
        self.lt = lt
        self.rt = rt
    def __str__(self):
        return "(%s %s %s)" % (self.lt, self.__class__.OPERATOR, self.rt)

class Plus(BinaryOperation):
    OPERATOR = "+"

class Minus(BinaryOperation):
    OPERATOR = "-"

class Multiply(BinaryOperation):
    OPERATOR = "*"

class Divide(BinaryOperation):
    OPERATOR = "/"

class Primary(Expression):
    pass

class Symbol(Primary):
    def __init__(self, name):
        self.name = name
    def __str__(self):
        return self.name

print Symbol("a")+Symbol("b")*Symbol("e")-Symbol("c")/Symbol("d")
print (Symbol("a")+Symbol("b"))*Symbol("e")-Symbol("c")/Symbol("d")
print (Symbol("a")+Symbol("b")*Symbol("e")-Symbol("c"))/Symbol("d")