Will Python execute finally block after receiving Ctrl+C

Question

If you stop a python script with Ctrl+C, will it execute any finally blocks, or will it literally stop the script where it is?

Answer 1

Well, the answer is mostly it depends. Here is what actually happens:

• Python executes code in a try:... finally: block
• a Ctrl-C is emitted and is translated in a KeyboardInterrupt Exception
• processing is interrupted and controls passes to the finally block

So at first sight, all works as expected. But...

When a user (not you, but others...) wants to interrupt a task he generally hits multiple times Ctrl-C. The first one will branch execution in the finally block. If another Ctrl-C occurs in the middle of the finally block because it contains slow operations like closing files, a new KeyboardInterrupt will be raised and nothing guarantees that the whole block will be executed, and you could have something like:

Traceback (most recent call last):
  File "...", line ..., in ...
    ...
KeyboardInterrupt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "...", line ..., in ...
    ...
  File "...", line ..., in ...
    ...
KeyboardInterrupt

Answer 2

Yes, assuming a single Ctrl+C, at least under Linux it will. You can test it with the following Python 3 code:

import time

try:
    print('In try.')
    time.sleep(1000)
finally:
    print('  <-- Note the Ctrl+C.')
    for i in range(1, 6):
        print(f'Finishing up part {i} of 5.')
        time.sleep(.1)

Here is the output:

$ ./finally.py
In try.
^C  <-- Note the Ctrl+C.
Finishing up part 1 of 5.
Finishing up part 2 of 5.
Finishing up part 3 of 5.
Finishing up part 4 of 5.
Finishing up part 5 of 5.
Traceback (most recent call last):
  File "./finally.py", line 7, in <module>
    time.sleep(1000)
KeyboardInterrupt

Answer 3

Yes, it will usually raise a KeyboardInterrupt exception, but remember that your application can be unexpectedly terminated at any time, so you shouldn't rely on that.