拒绝懒惰的家

class ICarnegieInfo:
    #single pattern by inner class
    class __single:
        def __init__(self):
            ICarnegieInfo.address = "nwpu"
            ICarnegieInfo.email = "tinylee@mail.com"
            ICarnegieInfo.instance = "instance"
            ICarnegieInfo.name = "tinylee"
            ICarnegieInfo.telephone = "87654321"
            ICarnegieInfo.url = "www.orchidy.com "
    instance = None

    def __init__(self):
        if not ICarnegieInfo.instance:
            ICarnegieInfo.instance = ICarnegieInfo.__single()
        else:
            return ICarnegieInfo.instance
    def getAddress(self):
        return self.address
    def getEmail(self):
        return self.email
    def getInstance(self):
        return self.name
    def getTelephone(self):
        return self.telephone
    def getUrl(self):
        return self.url

class ICarnegieApp:
    def do(self):
        handle = ICarnegieInfo()
        while True:
            try:
                str = int(raw_input('\n0 Exit\n'
                '1 Address\n'
                '2 Email\n'
                '3 Instance\n'
                '4 Telephone\n'
                '5 Url\n'
                'Input your Choice>'));
            except ValueError:
                print "You should input a Integer."
                continue
            if str < 0 or str > 5:
                print "Invalid input"
                continue
            elif str == 0:
                break
            elif str == 1:
                ret = handle.getAddress()
            elif str == 2:
                ret = handle.getEmail()
            elif str == 3:
                ret = handle.getInstance()
            elif str == 4:
                ret = handle.getTelephone()
            elif str == 5:
                ret = handle.getUrl()
            print ret
           
#main
app = ICarnegieApp()
app.do()

　 这个练习的目的：使用基本的循环和控制语句，使用单件模式，使用简单的异常处理。
需要注意的地方：
1。类名.属性名，表示该属性是类属性。所以在__single类中访问instance，需要加上ICarnegieInfo
2。方法定义的时候，如果有返回值，需要加上return语句，否则返回None，这个和java相同，和ruby不同。
3。从键盘中读取内容的方法：raw_input(''),但是会保留最后的回车。
   从控制台输出的方法：print
4。捕捉类型转换的异常是ValueError。
5。相邻的字符串连接的时候，可以不用+