Python 定位字符串

一位朋友在玩闯关游戏时遇到如下问题：

感觉考查的就是字符串操作，用string模块就可完成；代码如下：

# -*- coding: utf-8 -*-

__author__ = 'Evilxr'

import string

_string =("Vm0wd2QyUXlVWGxWV30d4WFlURn164dVRlpzWkc5V"
    "1JteDBaVVYwV0ZKdGVGWlZiVFZyVmxVeFY3yTkljRmhoTVhCU"
    "VZtcEdZV015U2tWVWJHaG9UVlZ3VlZadGNFZFRNbEpJVm10V1"
    "VtSk3lRazlVVkVKTFUFAceB00BxWmtWMXBFVWxwV01ERTBWMn"
    "RvUjFWdF55NsWlhiR2hYWVd0d2RscFdXbUZrUjA1R1drWndWM"
    "DFFUlRGV1ZFb3dWakZhV0ZOcmFHaFNlbXhXVm0weGIxSkdXbG"
    "RYYlVaclVqRmFTRll5TVRSVk1rcElaSHBDVjAxdVVuWldha3B"
    "IWXpGT2RWVnNXbWxoTUhCWl4A4YxWlNSMlF52UmtkWGEyUllZ"
    "bGhT5V0ZSV1pGTk5SbFowWlVaT1ZXSkdjREZWVjNoelZqRmFO"
    "bEZZYUZaaGExcG9WakJhVDJOdFJrZFhiV3hUVFcxb2IxWnRjR"
    "U5pTVVWNFdrVmtXRmRIVWxsWmJHaFRZMVpTVjJGRlRsTmlSbk"
    "JaV2xWYVQxWlhTa2RqUm1oYVRVWktXRll3V21GU2JFNTBZVVp"
    "44rYUdFeGNHOVdha0poVXpGa1dGSnJaR2hTTW1oUFZGY3hiMW"
    "RzV1hoWGJFNVRUVlp3TUZadGRHdFdNa3B6VTIxR1ZWWjZWblp"
    "XUkVaVFZteGtjbHBIY0U1V2EzQlhWbFprTkZNeFRYaFhhMXBQ"
    "VmxacmJFMHdVU1V6UkElM0QlM0Q")
mark = 0
while mark < len(_string) - 8:
    # 构造字符串
    result = _string[mark: mark + 8]
    try:
        # 长度为8
        assert len(result) == 8
    except:
        print u'字符串长度不为8'
        break
    try:
        # 它的前两位是大写英文
        assert result[0] in string.ascii_uppercase
        assert result[1] in string.ascii_uppercase
        # 它的3、4位是小写英文
        assert result[2] in string.ascii_lowercase
        assert result[3] in string.ascii_lowercase
        # 它的第5位和第8位是同一个字符
        assert result[4] == result[7]
        # 它的第6、7位是数字
        assert result[5] in string.digits
        assert result[6] in string.digits

        print 'success', result
        break
    except:
        mark = mark +1

　　

运行结果：

success FAceB00B