Python Signal Module
The signal module provides mechanisms to use signal handlers in Python. Signals are software interrupts delivered to a process by the operating system.
Importing the Module
import signal
import sys
import timeHandling Signals
To handle a signal, you define a handler function. This function takes two arguments: the signal number and the current stack frame.
def signal_handler(sig, frame):
print('You pressed Ctrl+C!')
sys.exit(0)Registering a Handler
Use signal.signal() to register a handler for a specific signal.
# Register the handler for SIGINT (Ctrl+C)
signal.signal(signal.SIGINT, signal_handler)
print('Press Ctrl+C')
while True:
time.sleep(1)Common Signals
signal.SIGINT: Interrupt from keyboard (Ctrl+C).signal.SIGTERM: Termination signal.signal.SIGKILL: Kill signal (cannot be caught or ignored).signal.SIGALRM: Timer signal (Unix only).
Alarms (Unix Only)
On Unix-based systems, you can use signal.alarm() to schedule a SIGALRM signal.
def handler(signum, frame):
raise Exception("Timeout")
# Register the signal function handler
signal.signal(signal.SIGALRM, handler)
# Define a 2-second alarm
signal.alarm(2)
try:
time.sleep(10)
except Exception as exc:
print(exc)Ignoring Signals
You can ignore a signal by setting the handler to signal.SIG_IGN.
signal.signal(signal.SIGINT, signal.SIG_IGN)