balance de parentesis

#!/usr/bin/env python

import sys

def parentesis(data):
    stack=[]
    for p in data:
        if p == '(':
            stack.append(p)
        elif p == ')':
            if len(stack) == 0:
                return False
            stack.pop(-1)
        else:
            raise Exception("simbolo invalido: " + str(p))
    return len(stack) == 0

def parentesis2(data):
    stack=[]
    f={'(': (lambda x: stack.append(x)), ')': (lambda x: stack.pop(-1))}
    try:
        map(lambda x: f[x](x), data)
    except IndexError:
        return False
    return len(stack) == 0

def parentesis3(data):
    valores = [x == '(' and 1 or -1 for x in data]
    tmp=0
    for x in valores:
        if tmp < 0: return False
        tmp += x
    return tmp==0

def parentesis4(data):
    return 0 == reduce(lambda a, b: a < 0 and (-2*len(data)) or a + b, [x == '(' and 1 or -1 for x in data], 0)

print parentesis4(sys.argv[1])