How Does PySerial Behave When the Connected Serial Device is Unplugged?

What will you learn?

In this guide, you will delve into the behavior of PySerial when a connected serial device is unexpectedly disconnected. You’ll explore strategies to handle such scenarios effectively, ensuring robust error handling and application stability.

Introduction to Problem and Solution

Working with serial communication in Python using PySerial simplifies tasks, but unplugging or turning off the connected serial device can lead to unhandled exceptions or unexpected behaviors. This guide aims to address these challenges by examining how PySerial responds to disconnections and implementing reliable error-handling mechanisms.

By understanding PySerial’s behavior in response to hardware disconnections, you’ll be equipped to detect these events and maintain application stability even in adverse conditions.


import serial
from time import sleep

# Connect to the serial device (adjust parameters as needed)
ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)

    while True:
        if ser.isOpen():
            print("Reading from the serial port")
            response = ser.readline().decode('utf-8').rstrip()
            print(f"Received: {response}")
            print("The serial port is closed")

        sleep(1)  # For demonstration purposes

except (serial.SerialException, OSError) as e:
    print(f"Error: {e}. The device may have been removed.")

# Copyright PHD


The code snippet showcases a loop for interacting with a serial device using PySerial. Here’s a breakdown:

  • Try-except Block: Essential for capturing I/O operation exceptions on the port.

  • isOpen() Method: Checks if the port is open before read/write operations.

  • Exception Handling: Catches serial.SerialException and OSError for graceful disconnection handling.

  • Cleanup in finally Block: Properly closes the port post-operation.

This example lays the foundation for managing sudden disconnections but can be customized based on project requirements.

    What is PySerial used for?

    PySerial facilitates interaction with serial ports in Python applications.

    How can I install PySerial?

    You can install it via pip: pip install pyserial.

    Can PySerial work with USB devices?

    Yes, if they emulate a COM port over USB.

    How do I list available COM ports on my system using PySerial?

    Utilize provided by PySerial.

    What does baud rate signify?

    It denotes the speed of data transmission over a communication channel.

    How do you handle timeouts in PySerial?

    Set timeouts during connection opening through the timeout parameter in serial.Serial() constructor.


    Mastering how PySerial behaves upon unexpected events like hardware disconnections demands knowledge of library operations and robust error-handling practices. By implementing these strategies effectively, even unforeseen issues such as abrupt disconnects can be managed seamlessly, ensuring optimal application performance.

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