《数据结构与算法Python语言描述》习题第二章第一题（python版）

题目：
定义一个表示时间的类Time
a)Time(hours,minutes,seconds)创建一个时间对象；
b)t.hours(),t.minutes(),t.seconds()分别返回时间对象t的小时，分钟和秒值
c)为Time对象定义加法和减法操作（用运算符+和-）
d)定义时间对象的等于和小于关系对象（用运算符==和<）

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-

 """
 定义一个表示时间的类Time
 a)Time(hours,minutes,seconds)创建一个时间对象；
 b)t.hours(),t.minutes(),t.seconds()分别返回时间对象t的小时，分钟和秒值
 c)为Time对象定义加法和减法操作（用运算符+和-）
 d)定义时间对象的等于和小于关系对象（用运算符==和<）

 ADT Time:                                           #定义时间的抽象数据类型
     Time(self, int hours, int minutes, int seconds) #构造时间对象
     +(self, Time t2)                                #求出本对象加t2的结果
     -(self, Time t2)                                #求出本对象减t2的结果
     ==(self, Time t2)                               #本对象是否和t2相等
     <(self, Time t2)                                #本对象小于t2
     hours(self)                                     #取出本对象的小时
     minutes(self)                                   #取出本对象的分钟
     seconds(self)                                   #取出本对象的秒值
 """
 """
 Author: Minion Xu
 Time:2016-11-21
 """

 class Time(object):
     __slots__ = ('_hours','_minutes','_seconds')

     #创建时间对象
     def __init__(self,  hours=0, minutes=0, seconds=0):
         #类型判断
         if not isinstance(hours, int) or not isinstance(minutes, int) or not isinstance(seconds, int):
             raise TypeError

         if(0<=hours<=23):
             self._hours   = hours
             if (0 <= minutes <= 59):
                 self._minutes = minutes
                 if (0 <= seconds <= 59):
                     self._seconds = seconds
                 else:
                     raise ValueError("%d is not valid seconds!" % seconds)
             else:
                 raise ValueError("%d is not valid minutes!" % minutes)

         else:
             raise ValueError("%d is not valid hours!" % hours)

     # +
     def __add__(self, other):
         seconds_add = self._seconds + other._seconds
         seconds_carry = seconds_add // 60    #超过60秒进位
         seconds = seconds_add % 60   #秒值
         minutes_add = self._minutes + other._minutes + seconds_carry
         minutes_carry = minutes_add // 60    #超过60分进位
         minutes = minutes_add % 60   #分钟
         hours_add = self._hours + other._hours + minutes_carry
         if(hours_add<24):
             hours = hours_add
         else:
             hours = hours_add - 24       #小时
         return Time(hours, minutes, seconds)
     # -
     def __sub__(self, other):
         if self._seconds < other._seconds:
             self._minutes -= 1
             seconds = self._seconds + 60 - other._seconds
         else:
             seconds = self._seconds - other._seconds
         if self._minutes < other._minutes:
             self._hours -= 1
             minutes = self._minutes + 60 - other._minutes
         else:
             minutes = self._minutes - other._minutes
         if self._hours < other._hours:
             hours = self._hours + 24 - other._hours
         else:
             hours = self._hours - other._hours
         return Time(hours, minutes, seconds)
     # ==
     def __eq__(self, other):
         bool1 = False
         bool2 = False
         bool3 = False
         if self._hours == other._hours:
             bool1 = True
         if self._minutes == other._minutes:
             bool2 = True
         if self._seconds == other._seconds:
             bool3 = True
         return bool1 and bool2 and bool3

     # <
     def __lt__(self, other):
         if self._hours < other._hours:
             return True
         elif self._hours == other._hours:
             if self._minutes < other._minutes:
                 return True
             elif self._minutes == other._minutes:
                 if self._seconds < other._seconds:
                     return True
                 else:
                     return False
             else:
                 return False
         else:
             return False

     def hours(self):
         return self._hours

     def minutes(self):
         return self._minutes

     def seconds(self):
         return self._seconds

     def print(self):
         print(self._hours,":",self._minutes,":",self._seconds)

     def __str__(self):
         return str(self._hours) + ":" + str(self._minutes) + ":" +str(self._seconds)

 if __name__ == '__main__':
     t = Time(21,31,59)
     t1 = Time(18,31,41)
     he = t + t1
     cha = t - t1
     print(he)
     print(cha)
     print(t==t1)
     print(t<t1)
     print(he.hours())