CODEWITHSUNDEEP
pythoncmdexittraceback
Stevoisiak
Stevoisiak

Reputation: 26752

Why is sys.exit() causing a traceback?

According to How to exit from Python without traceback?, calling sys.exit() in a Python script should exit silently without a traceback.

import sys
sys.exit(0)

However, when I launch my script from the command line on Windows 7 with python -i "exit.py", (or from Notepad++), a traceback for a SystemExit exception is displayed.

U:\>python -i "exit.py"
Traceback (most recent call last):
  File "exit.py", line 2, in <module>
    sys.exit(0)
SystemExit: 0
>>>

Why is sys.exit() displaying a traceback when run from the Windows command line?

(For reference, I am using Python 3.6.4 on Windows 7)

Upvotes: 6

Views: 11065

Answers (5)

Matt. Stroh
Matt. Stroh

Reputation: 914

As Matt_G says, sys.exit(0) is exactly the same as raising SystemExit(), which can be caught in higher level, which in your case is happening since you are using -i.

If you want to exit without traceback, there is os._exit(0) which calls a "C function" and exit immediately even in -i mode

as @user2357112 told me, os._exit(0) is drastic move that exits without any cleanup. No finally, __exit__, atexit, __del__, etc.

Upvotes: 1

Matt_G
Matt_G

Reputation: 516

Because under the hood, sys.exit(0) raises a SystemExit exception.

Further reading here

what you want is:

os._exit(1)

Upvotes: 1

Mike M&#252;ller
Mike M&#252;ller

Reputation: 85442

No exception shown:

python exit.py

and your program is terminated.

Run with -i option for interactive (inspect interactively after running script) and the exception is shown:

python -i exit.py 
Traceback (most recent call last):
  File "exit.py", line 2, in <module>
    sys.exit(0)
SystemExit: 0
>>>

because the interpreter keeps running.

exit([status])

Exit the interpreter by raising SystemExit(status).

Upvotes: 4

user2357112
user2357112

Reputation: 280456

You're running Python with the -i flag. -i suppresses the usual special handling of the SystemExit exception sys.exit raises; since the special handling is suppressed, Python performs the normal exception handling, which prints a traceback.

Arguably, -i should only suppress the "exit" part of the special handling, and not cause a traceback to be printed. You could raise a bug report; I didn't see any existing, related reports.

Upvotes: 9

pcarter
pcarter

Reputation: 1618

Because you are using the -i option. Try it without that and you won't get a stack trace.

$ python ptest.py
$ python -i ptest.py
Traceback (most recent call last):
  File "ptest.py", line 3, in <module>
    sys.exit(0)
SystemExit: 0

Upvotes: 0

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