It would be awfully nice (on posix platforms, for my use-case) to find out whether a file is inaccessible due to permission restrictions, or due to non-existence. Poking around in posixmodule.c, it seems os.access() uses posix_access(PyObject *self, PyObject *args), which calls _access/_waccess as described here: http://msdn.microsoft.com/library/en-us/vclib/html/_crt__access.2c_._wac cess.asp Run-Time Library Reference _access, _waccess Determine file-access permission. int _access( const char *path, int mode ); int _waccess( const wchar_t *path, int mode ); Parameters path File or directory path. mode Permission setting. Return Value Each function returns 0 if the file has the given mode. The function returns -1 if the named file does not exist or is not accessible in the given mode; in this case, errno is set as follows: EACCES Access denied: file's permission setting does not allow specified access. ENOENT Filename or path not found. ----------------- Here's the current posixmodule.posix_access (rev 2.329): static PyObject * posix_access(PyObject *self, PyObject *args) { char *path; int mode; int res; #ifdef Py_WIN_WIDE_FILENAMES if (unicode_file_names()) { PyUnicodeObject *po; if (PyArg_ParseTuple(args, "Ui:access", &po, &mode)) { Py_BEGIN_ALLOW_THREADS /* PyUnicode_AS_UNICODE OK without thread lock as it is a simple dereference. */ res = _waccess(PyUnicode_AS_UNICODE(po), mode); Py_END_ALLOW_THREADS return(PyBool_FromLong(res == 0)); } /* Drop the argument parsing error as narrow strings are also valid. */ PyErr_Clear(); } #endif if (!PyArg_ParseTuple(args, "si:access", &path, &mode)) return NULL; Py_BEGIN_ALLOW_THREADS res = access(path, mode); Py_END_ALLOW_THREADS return(PyBool_FromLong(res == 0)); } ----------------- It seems to me that, if EACCES and ENOENT were made available (in a future version of Python), I could solve my problem easily. One way would be to raise OSError within os.access if the result of _waccess == ENOENT, but this would cause problems with old code which depends upon the old behavior. Can we add an optional "error_if_not_found" arg to os.access? Return the result of _waccess instead of True/False? Make a new os function with the desired behavior? The next issue, then, is other platforms: is similar functionality available in OS/2, unix, etc.? Finally, if anyone has any immediate workarounds for me ;) answer in private or on c.l.p. Robert Brewer MIS Amor Ministries fumanchu@amor.org