Why Error is derived from EnvironmentError in shutil.py?

[Peng Yu]

I see Error is derived from EnvironmentError in shutil.py.

class Error(EnvironmentError):
pass

I'm wondering why EnvironmentError can not be raised directly. Why
Error is raised instead?

[Steven D'Aprano]

Probably to do with the personal taste of the author.

http://docs.python.org/library/shutil.html#shutil.Error

--
Steven

[alex23]

This way you can explicitly trap on shutil.Error and not intercept any
other EnvironmentError that might be raised.

And as it's a descendent of EnvironmentError, it can still be caught
by any handlers looking for such exceptions.

[Peng Yu]

It is true that an exception class is usually defined in a module and
all the exceptions raised in this module should be of this derived
class? Is it the general practice in python?

[Chris Rebert]

On Thu, Nov 12, 2009 at 7:10 AM, Peng Yu <peng...@gmail.com> wrote:
> On Thu, Nov 12, 2009 at 12:00 AM, alex23 <wuw...@gmail.com> wrote:

> It is true that an exception class is usually defined in a module and
> all the exceptions raised in this module should be of this derived
> class? Is it the general practice in python?

It is common, but not universal. Several of the modules in the stdlib
use the technique.

Cheers,
Chris
--
http://blog.rebertia.com