Difference between exit() and sys.exit() in Python

Question

In Python, there are two similarly-named functions, exit() and sys.exit(). What's the difference and when should I use one over the other?

Answer 1

exit is a helper for the interactive shell - sys.exit is intended for use in programs.

The site module (which is imported automatically during startup, except if the -S command-line option is given) adds several constants to the built-in namespace (e.g. exit). They are useful for the interactive interpreter shell and should not be used in programs.

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Technically, they do mostly the same: raising SystemExit. sys.exit does so in sysmodule.c:

static PyObject * sys_exit(PyObject *self, PyObject *args) {     PyObject *exit_code = 0;     if (!PyArg_UnpackTuple(args, "exit", 0, 1, &exit_code))         return NULL;     /* Raise SystemExit so callers may catch it or clean up. */     PyErr_SetObject(PyExc_SystemExit, exit_code);    return NULL; } 

While exit is defined in site.py and _sitebuiltins.py, respectively.

class Quitter(object):     def __init__(self, name):         self.name = name     def __repr__(self):         return 'Use %s() or %s to exit' % (self.name, eof)     def __call__(self, code=None):         # Shells like IDLE catch the SystemExit, but listen when their         # stdin wrapper is closed.         try:             sys.stdin.close()         except:             pass         raise SystemExit(code) __builtin__.quit = Quitter('quit') __builtin__.exit = Quitter('exit') 

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Note that there is a third exit option, namely os._exit, which exits without calling cleanup handlers, flushing stdio buffers, etc. (and which should normally only be used in the child process after a fork()).

Answer 2

If I use exit() in a code and run it in the shell, it shows a message asking whether I want to kill the program or not. It's really disturbing. See here

But sys.exit() is better in this case. It closes the program and doesn't create any dialogue box.