[Python-ideas] except expression

[Ethan Furman]

On 02/18/2014 07:25 AM, Chris Angelico wrote:
> On Wed, Feb 19, 2014 at 2:13 AM, MRAB <python at mrabarnett.plus.com> wrote:
>> Another possibility would be to say that a bare except in an expression
>> catches only certain "expression-oriented" exceptions, e.g. ValueError.
>> The simplest way to do that would be to make them subclasses of an
>> ExpressionError class. The question then becomes one of which
>> exceptions are "expression-oriented"...
>
> Easier than fiddling with class inheritance would be to make
> ExpressionError into a tuple of exception types - at least for testing
> purposes. If this _is_ to be done, I would definitely advocate having
> that name (or some equivalent) as a built-in, so it's straight-forward
> to either manipulate it or use it in a statement-except. But you're
> absolutely right that the question of which ones are
> expression-oriented would be a big one. I could imagine catching
> (ValueError, Unicode{En,De}codeError, AttributeError, EOFError,
> IOError, OSError, LookupError, NameError, ZeroDivisionError) and
> that's just from a quick skim of the built-in names. Would you
> consider making a tuple like that and then using "except
> CommonErrors:" all over your code? Or more to the point, if it were
> really convenient to do that, would it improve your code?

If you're catching that many exceptions, you may as well just use a bare except.  And be prepared to mask bugs.

--
~Ethan~