How to Avoid RuntimeError When Using threading.Timer in Python?

Threading.Timer: Repeating Functions at Specified Intervals

When working with Python threads, particularly when attempting to start and stop a timer repeatedly, understanding their behavior is crucial. One common challenge encountered while using threading.Timer is receiving a RuntimeError.

The Runtime Error:

The RuntimeError occurs when attempting to start a timer that has already been started. This is because threads, once started, cannot be restarted directly.

Workaround:

To address this issue, consider using a dedicated thread to handle the timer function. Here's how you can approach it:

Creating a Timer Thread:

Use a custom thread class (MyThread) that inherits from Thread and incorporates the timer logic.

import threading

class MyThread(threading.Thread):
    def __init__(self, event):
        Thread.__init__(self)
        self.stopped = event

    def run(self):
        while not self.stopped.wait(0.5):
            print("my thread")
            # call your function here

Starting and Stopping the Timer:

In the code that initiates the timer, create a stopFlag event and use it to signal when the timer should stop.

stopFlag = threading.Event()
thread = MyThread(stopFlag)
thread.start()  # Start the timer thread once
# To stop the timer, set the stopFlag event
stopFlag.set()

Advantages of this Approach:

• The timer thread is started only once, avoiding the RuntimeError.
• The timer function is executed on a separate thread, preventing it from blocking the main thread.
• Accurate and consistent time intervals are maintained, even during heavy processing.

The above is the detailed content of How to Avoid RuntimeError When Using threading.Timer in Python?. For more information, please follow other related articles on the PHP Chinese website!