Does python's `os.system` ever throw an exception?

Might the esteemed os.system of Python fame开发者_StackOverflow throw an exception? If so, which ones?

Short answer: yes:

>>> import os
>>> os.system(None)
TypeError ...

Long answer: look here http://docs.python.org/library/subprocess.html#subprocess-replacements to see how to avoid using os.system.

On POSIX systems it appears to be a straight pass-through to system() (listing from Python 2.7.1's posixmodule.c):

static PyObject *
posix_system(PyObject *self, PyObject *args)
{
    char *command;
    long sts;
    if (!PyArg_ParseTuple(args, "s:system", &command))
        return NULL;
    Py_BEGIN_ALLOW_THREADS
    sts = system(command);
    Py_END_ALLOW_THREADS
    return PyInt_FromLong(sts);
}

os.system throws a TypeError if there is not exactly one string argument. If the fork fails due to resource or ulimit restrictions, it will return -1. If the argument is not valid in some way (like non-existing command), it will return a high error code. Apart from the aforementioned TypeError, os.system does not throw any exceptions.

If you're asking whether it throws an exception when the process you're calling ends with an error, the answer is no, you can call a program with os.system(), have it error out, and you will never know.

That's why you should use the subprocess module.