python中的前缀表示法解析 [英] prefix notation parsing in python

问题描述

马上开始-不，这不是功课.

Right off the bat - no, this is NOT homework.

例如，我想在python中编写一个前缀符号解析器(目前为总和)...

I would like to write a prefix notation parser in python (for sums presently)... for example

如果给出:+ 2 2，它将返回:4

if given: + 2 2 it would return: 4

想法?

推荐答案

def prefix(input):
  op, num1, num2 = input.split(" ")
  num1 = int(num1)
  num2 = int(num2)
  if op == "+":
    return num1 + num2
  elif op == "*":
    return num1 * num2
  else:
    # handle invalid op
    return 0

print prefix("+ 2 2")

打印4，还包括一个乘法运算符，只是为了展示如何扩展它.

prints 4, also included a multiplication operator just to show how to expand it.

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