think python 第16章 classes and functions

16.1 time

16.2pure functions

编写两个函数，实现时间相加功能。

class Time(object):
    '''指代时间
    属性：hour,minute,second'''
time = Time()
def add_time(t1,t2):
    sum = Time()
    sum.hour = t1.hour + t2.hour
    sum.minute = t1.minute + t2.minute
    sum.second = t1.second + t2.second
　　 if sum.second >= 60:
        sum.second -= 60
        sum.minute += 1
    if sum.minute >= 60:
        sum.minute -= 60
        sum.hour += 1
    return sum

def print_time(time):
    print("%.2d"% time.hour +":"
          + "%.2d"% time.minute + ":"
          + "%.2d"% time.second)

测试：

>>> s = Time()
>>> s.hour = 9
>>> s.minute = 45
>>> s.second = 0
>>> dur = Time()
>>> dur.hour = 1
>>> dur.minute = 35
>>> dur.second = 0
>>> done = add_time(s,dur)
>>> print_time(done)
11:20:00

16.3modifiers

16.4prototyping versus planning(原型设计与计划)

其实就是将问题普遍化看似将问题复杂化，有时却简化了问题（因为特殊情况变少，出错概率也降低）