Prefix notation math interpreter.

prefix.py

def gen(data):
    def g():
        for token in data.split(" "):
            yield token
    return g().next


defs = {"+": lambda x, y: x + y,
        "-": lambda x, y: x - y,
        "*": lambda x, y: x * y,
        "/": lambda x, y: x / y}

def parser(data):
    op = data()
    if op not in defs:
        return op
    val1 = int(parser(data))
    val2 = int(parser(data))
    return defs[op](val1, val2)

import sys
data = sys.stdin.readline().strip()
print parser(gen(data))