python中exit()和sys.exit()的区别

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

在python中，有两个同名的函数：exit()和sys.exit()。有什么区别？我什么时候应该用一个？

exit是交互式shell的助手—sys.exit用于程序中。

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.

从技术上讲，他们做的基本相同：提高SystemExit。sys.exit在sysmodule.c中这样做：

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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;
}

而exit分别在site.py和sitebuiltins.py中定义。

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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')

请注意，还有第三个退出选项，即os._exit，它在不调用清理处理程序、刷新stdio缓冲区等的情况下退出(通常只在fork()之后的子进程中使用)。