Just a random mockup of a postfix evaluator

postfix.py

from operator import *
def isInt(x):
    try:
        a = float(x)
        b = int(a)
    except ValueError:
        return False
    else:
        return a == b
def Postfix(exp):
    ops, stack = {'~':(inv,1),'!':(not_,1),'*':(mul,2),'/':(div,2),'%':(mod,2),'+':(add,2),'-':(sub,2),'&':(and_,2),'^':(xor,2),'|':(or_,2)}, []
    for t in exp.split(' '):
        if all(map(lambda x:x in "1234567890.",t)):
            stack.append(int(float(t)) if isInt(t) else float(t))
        else:
            if t in ops:
                f, n = ops[t]
                if len(stack) >= n:
                    stack.append(f(*[stack.pop() for i in range(n)][::-1]))
                else:
                    print "Error, pop from empty stack"
            else:
                print "Error, non-recognized character:",t
    return stack[0] if len(stack) == 1 else stack