gistfile1.py

import re

# input is a list of tokens (token is a number or operator)
tokens = raw_input()

# remove whitespace
tokens = re.sub('\s+', '', tokens)

# split by addition/subtraction operators
tokens = re.split('(-|\+)', tokens)

# takes in a string of numbers, *s, and /s. returns the result
def solve_term(tokens):
    tokens = re.split('(/|\*)', tokens)
    ret = float(tokens[0])
    for op, num in zip(tokens[1::2], tokens[2::2]):
        num = float(num)
        if op == '*':
            ret *= num
        else:
            ret /= num
    return ret

# initialize final result to the first term's value
result = solve_term(tokens[0])

# calculate the final result by adding/subtracting terms
for op, num in zip(tokens[1::2], tokens[2::2]):
    result +=  solve_term(num) * (1 if op == '+' else -1)

print result