calculator.py 文件源码

def evaluateStack( s ):
    try:
        op = s.pop()
        if op == 'unary -':
            return -evaluateStack( s )
        if op in "+-*/^":
            op2 = evaluateStack( s )
            op1 = evaluateStack( s )
            return opn[op]( op1, op2 )
        elif op == "PI":
            return math.pi # 3.1415926535
        elif op == "E":
            return math.e  # 2.718281828
        elif op in fn:
            return fn[op]( evaluateStack( s ) )
        elif op[0].isalpha():
            return 0
        else:
            return float( op )
    except:
        return None