python下timer定时器常用的两种实现方法

方法一，使用线程中现成的：

  这种一般比较常用，特别是在线程中的使用方法，下面是一个例子能够很清楚的说明它的具体使用方法：

#! /usr/bin/python3
#! -*- conding: utf-8 -*-
import threading
import time
def fun_timer():
    print(time.strftime('%Y-%m-%d %H:%M:%S'))
    global timer
    timer = threading.Timer(2,fun_timer)
    timer.start();
timer = threading.Timer(1,fun_timer)
timer.start();
time.sleep(5)
timer.cancel()
print(time.strftime('%Y-%m-%d %H:%M:%S'))

方法二，根据time中的来定义timer：

  这种方法使用比较灵活，可根据自身的东西来添自身的需求：

import time

class TimerError(Exception):
    """A custom exception used to report errors in use of Timer class"""

class Timer:
    def __init__(self):
        self._start_time = None

    def start(self):
        """Start a new timer"""
        if self._start_time is not None:
            raise TimerError(f"Timer is running. Use .stop() to stop it")

        self._start_time = time.perf_counter()

    def stop(self):
        """Stop the timer, and report the elapsed time"""
        if self._start_time is None:
            raise TimerError(f"Timer is not running. Use .start() to start it")

        elapsed_time = time.perf_counter() - self._start_time
        self._start_time = None
        print(f"Elapsed time: {elapsed_time:0.4f} seconds")