python时钟的实现

from time import sleep
import time
import os

class Clock(object):
    """数字时钟"""

    def __init__(self, hour=0, minute=0, second=0):
        """初始化方法

        :param hour: 时
        :param minute: 分
        :param second: 秒
        """
        self._hour = hour
        self._minute = minute
        self._second = second

    def run(self):
        """走字"""
        self._second += 1
        if self._second == 60:
            self._second = 0
            self._minute += 1
            if self._minute == 60:
                self._minute = 0
                self._hour += 1
                if self._hour == 24:
                    self._hour = 0

    def show(self):
        """显示时间"""
        return '%02d:%02d:%02d' % \
               (self._hour, self._minute, self._second)


def main():
    localtime = time.asctime( time.localtime(time.time()) )
    hour = int(localtime[11:13])
    min = int(localtime[14:16])
    sec = int(localtime[17:19])
    clock = Clock(hour, min, sec)
    while True:
        print(clock.show())
        sleep(1)
        clock.run()
        os.system('cls')


if __name__ == '__main__':
    main()

获取系统时间，

import time
localtime = time.asctime( time.localtime(time.time()) )

python中强制转换int型 

hour = int(localtime[11:13])

python中的字符串截取

str = ‘0123456789’
print str[0:3] #截取第一位到第三位的字符
print str[:] #截取字符串的全部字符
print str[6:] #截取第七个字符到结尾
print str[:-3] #截取从头开始到倒数第三个字符之前
print str[2] #截取第三个字符
print str[-1] #截取倒数第一个字符
print str[::-1] #创造一个与原字符串顺序相反的字符串
print str[-3:-1] #截取倒数第三位与倒数第一位之前的字符
print str[-3:] #截取倒数第三位到结尾
print str[:-5:-3] #逆序截取，具体啥意思没搞明白？

python清空终端

import os
os.system('cls')