Since WindowsError became an alias of OSError, the error number shown in the stringification of an OSError err can either be a windows error code (err.winerror) or a posix style error number (err.errno), with no way to tell which.

For instance in

  >>> os.read(999, 0)
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  OSError: [Errno 9] Bad file descriptor

err.errno == EBADF == 9 and err.winerror == None, but in

  >>> _winapi.ReadFile(999, 0)
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  OSError: [Error 6] The handle is invalid

err.errno == EBADF == 9 and err.winerror == ERROR_INVALID_HANDLE == 6.  (winerror gets priority over errno if it exists.)

With the attached patch the second will be shown as

  >>> _winapi.ReadFile(999, 0)
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  OSError: [WinError 6] The handle is invalid
            ^^^

Since this issue only applies to 3.3 and the patch is trivial, it would be nice to get this in before 3.3 is released.

I originally kept it that way to minimize disruption with 3.2, but I agree it's a welcome change. As for acceptance in 3.3, Georg will have to decide.

Uh, currently it's "Errno" or "Error", so there is a way to tell which.

I'll leave to Antoine to decide what to do here; it's not like changing it a big deal.

"WinError" looks kind of ugly to me though.

Well, "Error" and "Errno" are rather hard to distinguish, and the difference isn't obvious either, so Richard's patch is a good improvement IMHO.

> Well, "Error" and "Errno" are rather hard to distinguish

Embarrassingly, I did not even notice the was a difference.

New changeset 2e587b9bae35 by Richard Oudkerk in branch 'default':
Issue #15784: Modify OSError.__str__() to better distinguish between
http://hg.python.org/cpython/rev/2e587b9bae35

The changeset is 2e587b9bae35.

Georg, could you copy it to your release branch please.

Done in 4e941113e4fa.

New changeset 4e941113e4fa by Richard Oudkerk in branch 'default':
Issue #15784: Modify OSError.__str__() to better distinguish between
http://hg.python.org/cpython/rev/4e941113e4fa