python threading timer example
threading.Timer executes functions asynchronously after a specified delay without blocking the main thread, and is suitable for handling lightweight delays or periodic tasks. ① Basic usage: Create a Timer object and call the start() method to delay the execution of the specified function; ② Cancel the task: Calling the cancel() method before the task is executed can prevent execution; ③ Repeating execution: Enable periodic operation by encapsulating the RepeatingTimer class; ④ Notes: Each Timer starts a new thread, and resources should be managed reasonably. Call cancel() if necessary to avoid memory waste. When the main program exits, you need to pay attention to the influence of non-daemon threads. It is suitable for delayed operations, timeout processing, and simple polling. It is simple but very practical.
Python's threading.Timer is a very practical tool that allows you to execute a function after specifying a delay, and this execution is asynchronous (does not block the main thread). Below is a simple and easy-to-understand threading.Timer example, suitable for beginners to understand and use.
? Basic usage examples
import threading
def my_task():
print("The timing task has been executed!")
# Create a timer: execute my_task function timer = threading.Timer(5.0, my_task)
# Start timer timer.start()
print("The main thread continues to run...")Output effect:
The main thread continues to run... (Wait 5 seconds later) The scheduled task is executed!
✅ Note:
Timerruns in child threads, so it does not block the main thread.
? Cancel the timed task (important!)
Sometimes you may want to cancel the task before it is executed, such as the user operation changes the state.
import threading
import time
def my_task():
print("Task was executed!")
timer = threading.Timer(5.0, my_task)
timer.start()
print("Timer started")
# The simulation decides to cancel the task after 3 seconds time.sleep(3)
if timer.is_alive():
timer.cancel()
print("Timer cancelled")Output:
Timer is started (after 3 seconds) Timer cancelled
❗ If
cancel()is called beforerun(), the task will not be executed.
? Repeat the timing task (cycle timer)
Timer is executed only once by default. If you want it to run periodically, you can encapsulate it yourself:
import threading
class RepeatingTimer:
def __init__(self, interval, function, *args, **kwargs):
self.interval = interval
self.function = function
self.args = args
self.kwargs = kwargs
self.timer = None
self.is_running = False
def _run(self):
self.is_running = False
self.start() # Restart the timer self.function(*self.args, **self.kwargs) # Execute the task def start(self):
if not self.is_running:
self.timer = threading.Timer(self.interval, self._run)
self.timer.start()
self.is_running = True
def stop(self):
if self.timer is not None:
self.timer.cancel()
self.is_running = False
# Use example def says_hello():
print("Hello, I execute it every 2 seconds")
rt = RepeatingTimer(2.0, say_hello)
rt.start()
# Stop import time after running for 10 seconds
time.sleep(10)
rt.stop()
print("Timer stopped")? Common precautions
-
Timerinherits fromThread, so each timer will open a new thread. - If you create a large number of
Timerobjects, it may consume more resources. - Don't forget to call
cancel()to avoid unnecessary execution. - When the main program exits,
Timerof the non-daemon thread will prevent the program from exiting. You can settimer.daemon = True(but it is generally not recommended to set it at will).
Basically that's it. threading.Timer is suitable for lightweight, delayed or periodic tasks, such as:
- Delayed sending of messages
- Timeout processing (such as connection timeout)
- Simple polling or heartbeat mechanism
Not complicated, but very practical.
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