Question

I’m new to Python. I just want to know why the finally block is executing after calling sys.exit(0) in the except block?

Code:

import sys

def divide_by_zero():
    try:
        10/0
        print "It will never print"
    except Exception:
        sys.exit(0)
        print "Printing after exit"
    finally:
        print "Finally will always print"

divide_by_zero() 

Btw., I was just trying to do the same thing as in Java, where the finally block is not executed when System.exit(0) is in the catch block.

Answer 1

All sys.exit() does is raise an exception of type SystemExit.

From the documentation:

Exit from Python. This is implemented by raising the SystemExit
exception, so cleanup actions specified by finally clauses of try
statements are honored, and it is possible to intercept the exit
attempt at an outer level.

If you run the following, you’ll see for yourself:

import sys
try:
  sys.exit(0)
except SystemExit as ex:
  print 'caught SystemExit:', ex

As an alternative, os._exit(n) with the status code will stop the process bypassing much of the cleanup, including finally blocks etc.