inurface.py

#!/usr/bin/env python
# coding=utf-8

import sys, operator, re

OPMAP = {'+': operator.add, '-': operator.sub, '/': operator.div, '*': operator.mul}
RE_PARSE = re.compile(r'(?P<op>[+\-/\*])\s+(?P<num>\d+)')

def apply(line, prev):
    op, num = re.match(RE_PARSE, line.strip('\n')).groups()
    return OPMAP[op](prev, float(num))

def do(file_name):
    with open(file_name) as f:
        lines = f.readlines()
        operations = lines[:-1]
        base = float(lines[-1].split(' ')[1])

        return reduce(lambda x,y: apply(y, x), operations, base)

if __name__ == '__main__':
    print do(sys.argv[1])

+ 5
+ 20
- 15
/ 3
* 2
apply 5

starenka /tmp % python fap.py faps
10.0