[Python-Dev] Raising OSError concrete classes from errno code

[Antoine Pitrou]

On Wed, 26 Dec 2012 13:37:13 +0200
Andrew Svetlov <andrew.svetlov at gmail.com> wrote:
> >
> > As Serhiy's example shows, this mapping of error numbers to subclasses
> > is implemented directly in OSError.__new__. We did this so that code
> > could catch the new exceptions, even when dealing with old code that
> > raises the legacy exception types.
> >
> Sorry.
> Looks like OSError.__new__ requires at least two arguments for
> executing subclass search mechanism:
> 
> >>> OSError(errno.ENOENT)
> OSError(2,)
> >>> OSError(errno.ENOENT, 'error msg')
> FileNotFoundError(2, 'error msg')

Indeed, it does. I did this for consistency, because calling OSError
with only one argument doesn't set the "errno" attribute at all:

>>> e = OSError(5)
>>> e.errno
>>> 

Regards

Antoine.