Achieve python clock

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()

Get the system time,

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

int type cast in python 

hour = int(localtime[11:13])

String interception in python

= STR '0123456789 '
 print STR [0:. 3] # , taken first to third character 
print STR [:] # taken all the character string 
print STR [. 6:] # taken to the end of the seventh character 
print STR [: -. 3] # , taken from the beginning until the antepenultimate characters 
Print STR [2] # taken third character 
Print STR [-1] # taken penultimate character 
Print STR [:: -. 1] # creating a reverse order of the strings and the original string 
print STR [-3: -1] # taken characters and the bottom third of the penultimate one previous 
print STR [-3:] # taken countdown to the end of the third 
print str [: - 5: -3] # reverse the interception, did not thoroughly understand the specific what do you mean?

python empty terminal

import the 
os.system ( ' cis ' )