Python Timer cancel()用法及代码示例

Python Timer.cancel() 方法

cancel() 是 Python 中线程模块的 Timer 类的内置方法。

Timer 类对象代表必须在给定时间过后才能执行的操作。这个类是Thread类的子类。该类中的 Cancel() 方法用于停止定时器和取消定时器对象的执行。只有当计时器仍在等待区域时，动作才会停止。

模块：

    from threading import Timer

用法:

    cancel()

参数：

• None

返回值：

这个方法的返回类型是<class 'NoneType'>.该方法不返回任何内容。它用于在线程等待期间取消线程。

范例1：

# python program to explain the
# use of cancel() method in Timer class

import threading

def helper_function(i):
  print("Value printed=",i)

if __name__=='__main__':
    
  thread1 = threading.Timer(interval = 3, function = helper_function,args = (9,))
  print("Starting the timer object")
  print()
  
  # Starting the function after 3 seconds
  thread1.start()
  
  print("This gets printed before the helper_function as helper_function starts after 3 seconds")
  print()
  
  # This cancels the thread when 3 seconds 
  # have not passed
  thread1.cancel()
  print("Thread1 cancelled, helper_function is not executed")

输出：

Starting the timer object

This gets printed before the helper_function as helper_function starts after 3 seconds

Thread1 cancelled, helper_function is not executed

范例2：

# python program to explain the
# use of cancel() method in Timer class

import threading
import time

def helper_function(i):
  print("Value printed=",i)
  print()
  
if __name__=='__main__':
    
  thread1 = threading.Timer(interval = 3, function = helper_function,args = (19,))
  print("Starting the timer object")
  print()
  
  # Starting the function after 3 seconds
  thread1.start()
  # Sleeping this thread for 5 seconds
  time.sleep(5)
  
  # This will not cancel the thread as 3 seconds have passed
  thread1.cancel()
  print("This time thread is not cancelled as 3 seconds have passed when cancel() method is called")

输出：

Starting the timer object

Value printed= 19

This time thread is not cancelled as 3 seconds have passed when cancel() method is called