calculator.py 文件源码

def __init__(self, calc = SimpleCalculator()):
        self.exprStack = []

        def pushStack(s, l, t):
            self.exprStack.append(t[0])

        integer = Word(nums).addParseAction(pushStack)
        addop = Literal('+') | Literal('-')
        mulop = Literal('*') | Literal('/')
        lpar = Literal('(')
        rpar = Literal(')')

        expr = Forward()
        atom = integer | lpar + expr + rpar
        term = atom + ZeroOrMore((mulop + atom).addParseAction(pushStack))
        expr << term + ZeroOrMore((addop + term).addParseAction(pushStack))
        self.expr = expr + StringEnd()

        self.opfun = {
                '+' : (lambda a, b: calc.add(a,b)),
                '-' : (lambda a, b: calc.sub(a,b)),
                '*' : (lambda a, b: calc.mul(a,b)),
                '/' : (lambda a, b: calc.div(a,b)) }