How to compare two versions?

def ver_cmp(v1, v2):
    lst = map(lambda x, y: ((0 if not x else x), (0 if not y else y)),
              v1.split('.'), v2.split('.'))

    for num1, num2 in lst:
        if num1 != num2:
            if num1 > num2:
                return (1, 'greater')
            else:
                return (2, 'less')
    return (0, 'equal')

    # Example:
    #
    # >>> print ver_cmp('1.6.2', '1.6')
    # >>> (1, 'greater')