Raising a specific OSError

[David Hirschfield]

I know this should be obvious, but how does one raise a specific type of
OSError?
When I attempt to perform a file operation on a non-existent file, I get
an OSError: [Errno 2], but what if I want to raise one of those myself?

Thanks in advance,
-Dave

--
Presenting:
mediocre nebula.

[alisonken1]

Re: Raising a specific OSError


To raise a specific error, just find the error that you want to raise,
then give the error a text string to print: ex.

raise IOError("This raises an IO error")

On the stderr output, when the routine hits this line, you will get:
[color=blue][color=green][color=darkred]
>>> raise IOError("This raises an IOError")[/color][/color][/color]
Traceback (most recent call last):
File "<stdin>", line 1, in ?
IOError: This raises an IOError
[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

Just be sure of the error that you want to raise, since some of them
will do stuff like closing open file descriptors as well.

[Kelvie Wong]

Re: Raising a specific OSError

I do not see the point in doing so (why not just copy+paste that
string?), but the errno (specifically ENOENT) corresponds to the
POSIX.1 error number, and the string "No such file or directory" is
done in C via strerror(ENOENT ); (check errno(3) and strerror(3)).

I doubt there is something that does this in the standard library
(just checked, there's an errno module, but it is quite sparse), but a
simple C extension would be trivial to write.

However, the best way is just to copy and paste that text into your
program, I mean, why not?

raise OSError("[Errno 2] No such file or directory")

On 4/21/06, David Hirschfield <davidh@ilm.com > wrote:[color=blue]
> I wasn't clear enough in my original post.
>
> I know how to raise a basic OSError or IOError, but what if I want to raise
> specifically an "OSError: [Errno 2] No such file or directory"?
> Somehow it must be possible to raise the error with the correct information
> to bring up the standard message, but where do I find the right values to
> give?
>
> Thanks,
> -Dave
>
>
>
> alisonken1 wrote:
> To raise a specific error, just find the error that you want to raise,
> then give the error a text string to print: ex.
>
> raise IOError("This raises an IO error")
>
> On the stderr output, when the routine hits this line, you will get:
>
>
>
>
>
> raise IOError("This raises an IOError")
>
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> IOError: This raises an IOError
>
>
> Just be sure of the error that you want to raise, since some of them
> will do stuff like closing open file descriptors as well.
>
>
>
>
> --
> Presenting:
> mediocre nebula.
>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
>[/color]


--
Kelvie

[Kelvie Wong]

Re: Raising a specific OSError

Looking at the Python docs.. I found this:

http://docs.python.org/ext/errors.html

"""
Another useful function is PyErr_SetFromEr rno(), which only takes an
exception argument and constructs the associated value by inspection
of the global variable errno. The most general function is
PyErr_SetObject (), which takes two object arguments, the exception and
its associated value. You don't need to Py_INCREF() the objects passed
to any of these functions.
"""

So, in a C extension, to raise a a specific OSError...

errno = ENOENT;
PyErr_SetFromEr rno(PyExc_OSErr or);

should work...

On 4/21/06, Kelvie Wong <kelvie@ieee.or g> wrote:[color=blue]
> I do not see the point in doing so (why not just copy+paste that
> string?), but the errno (specifically ENOENT) corresponds to the
> POSIX.1 error number, and the string "No such file or directory" is
> done in C via strerror(ENOENT ); (check errno(3) and strerror(3)).
>
> I doubt there is something that does this in the standard library
> (just checked, there's an errno module, but it is quite sparse), but a
> simple C extension would be trivial to write.
>
> However, the best way is just to copy and paste that text into your
> program, I mean, why not?
>
> raise OSError("[Errno 2] No such file or directory")
>
> On 4/21/06, David Hirschfield <davidh@ilm.com > wrote:[color=green]
> > I wasn't clear enough in my original post.
> >
> > I know how to raise a basic OSError or IOError, but what if I want to raise
> > specifically an "OSError: [Errno 2] No such file or directory"?
> > Somehow it must be possible to raise the error with the correct information
> > to bring up the standard message, but where do I find the right values to
> > give?
> >
> > Thanks,
> > -Dave
> >
> >
> >
> > alisonken1 wrote:
> > To raise a specific error, just find the error that you want to raise,
> > then give the error a text string to print: ex.
> >
> > raise IOError("This raises an IO error")
> >
> > On the stderr output, when the routine hits this line, you will get:
> >
> >
> >
> >
> >
> > raise IOError("This raises an IOError")
> >
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in ?
> > IOError: This raises an IOError
> >
> >
> > Just be sure of the error that you want to raise, since some of them
> > will do stuff like closing open file descriptors as well.
> >
> >
> >
> >
> > --
> > Presenting:
> > mediocre nebula.
> >
> >
> > --
> > http://mail.python.org/mailman/listinfo/python-list
> >
> >[/color]
>
>
> --
> Kelvie
>[/color]


--
Kelvie

[Lawrence D'Oliveiro]

Re: Raising a specific OSError

In article <mailman.4855.1 145658087.27775 .python-list@python.org >,
David Hirschfield <davidh@ilm.com > wrote:
[color=blue]
>When I attempt to perform a file operation on a non-existent file, I get
>an OSError: [Errno 2], but what if I want to raise one of those myself?[/color]

raise OSError(2, "No such file or directory")