Objective     record

1 threading.Timer

1.1 threading.Timer structure

1.1.1 threading.Timer Constructors

1.1.2 parameter list

1.2 threading.Timer Properties and methods

1.3 threading.Timer Use demonstration

1.3.1 Simple deferred call

1.3.2  Call as a timer

1.3.3 The advantage of loop calling over starting a batch of threads at the same time

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Python Multithreaded programming Directory

Python Multithreaded programming -01-threading The module first

Python Multithreaded programming -02-threading modular - Use of locks

Python Multithreaded programming -03-threading modular - Condition

Python Multithreaded programming -04-threading modular - Event

Python Multithreaded programming -05-threading modular - Semaphore and BoundedSemaphore

1 threading.Timer

     threading.Timer yes threading.Thread A derived class of , At the appointed time n Execute a function function in seconds . It will integrate threading.Thread Many properties and methods of .

      Timer The source code implementation of is very simple , After receiving a task , Creates a thread , The thread logic is inserted at the front sleep. If you think about it , When there are many tasks , Context switching is also a resource consuming thing , You don't have to .

1.1 threading.Timer structure

1.1.1 threading.Timer Constructors

        timer=threading.Timer(interval, function, args=None, kwargs=None)

1.1.2 parameter list

1. interval： In seconds , Indicates how long the thread starts
2. function： Indicates what function the thread wants to call , What functions are performed
3. args： Apply to function Parameter list for
4. kwargs： Apply to function Parameter dictionary for

1.2 threading.Timer Properties and methods

        Basically   threading.Thread Properties and methods of , threading.Timer There are , Please refer to the previous article for details  Python Multithreaded programming -01-threading The module first 2.1.1 Section .

        besides , It also has some special methods .

threading.Timer Properties and methods Serial number Properties and methods describe 1 attribute args Apply to function Parameter list for 2 attribute interval In seconds , Indicates how long the thread starts 3 attribute  kwargs Apply to function Parameter dictionary for 4 Method stop() If this Timer It's not over yet , Then it ends .

        Another one threading.Timer object , If the .finished() Method , Is to get a threading.Event Class object . 

1.3 threading.Timer Use demonstration

1.3.1 Simple deferred call

Here is a piece of code , I hope to print out in turn words In the list word, The delay time per thread depends on word The length of , And every time you print word Print the current time before .

import threading
import time
words=["a","12"," Hello ！"," The spring breeze miles "]
timer_list=[]
def show_time_on_word(word):
print(time.ctime()+"==>"+word)
for word in words:
timer=threading.Timer(len(word)*10,show_time_on_word,args=[word])
timer_list.append(timer)
for timer in timer_list:
timer.start()

The operation results are as follows ：

 

1.3.2  Call as a timer

Want to run a piece of code , every other 10 Second time reporting , Cumulative time reporting 10 Time .

import threading
import time
count=0
def show_time():
print("Coming in show time!")
global count
if(count<10):
count+=1
print(time.ctime())
create_timer()
else:
print("All done!")
def create_timer():
timer=threading.Timer(10,show_time)
timer.start()
print(time.ctime()," Starting !")
create_timer()

Running results

  

 

1.3.3 The advantage of loop calling over starting a batch of threads at the same time

1.3.2 It is mainly generated by circular call Timer, and 1.3.1 Is to generate a batch of threads at the same time . By comparison , Loop calls are better , By calling threading.active_count() It can be seen that , There is no need for multiple maintenance threads .