KeyboardInterrupt

Traceback

terminal

Traceback (most recent call last):
  File "main.py", line 2, in <module>
    data = process_batch()  # Ctrl+C kills immediately, losing work
KeyboardInterrupt

What causes this error

The user pressed Ctrl+C (or sent SIGINT on Unix) to interrupt the running program.

How to fix it

Use try/except KeyboardInterrupt for graceful shutdown. Save partial work in a finally block. For long-running processes, implement signal handlers with the `signal` module for more control.

Code that causes this error

Broken

while True:
    data = process_batch()  # Ctrl+C kills immediately, losing work

Fixed code

Fixed

try:
    while True:
        data = process_batch()
        save_checkpoint(data)
except KeyboardInterrupt:
    print("\nInterrupted — saving progress...")
    save_checkpoint(data)

About KeyboardInterrupt

KeyboardInterrupt is raised when the user presses Ctrl+C (or the interrupt key for their platform). Like SystemExit, it inherits from BaseException rather than Exception, so `except Exception` does not catch it. This design ensures that users can always abort a running program.

KeyboardInterrupt can happen at almost any point during execution, which makes it important for long-running code to handle it gracefully — for example, saving partial results, closing network connections, or cleaning up temporary files. Use try/except KeyboardInterrupt or try/finally blocks to implement graceful shutdown. In asyncio code, KeyboardInterrupt works differently and may need special handling.

The `signal` module provides lower-level control over interrupt handling if you need to defer or customize the interrupt behavior.

Common scenarios

Infinite recursion from missing or incorrect base cases

Modifying dictionaries or sets during iteration

Calling generators or coroutines in unsupported ways

Using asyncio event loops incorrectly or attempting to nest them