[Python-ideas] except expression

[Steven D'Aprano]

On Wed, Feb 19, 2014 at 01:52:30AM +0000, Rob Cliffe wrote:
> 
> On 18/02/2014 23:43, Ethan Furman wrote:
> >On 02/18/2014 03:27 PM, Steven D'Aprano wrote:
> >>
> >>-1 on bare excepts in the expression form.
> >
> >Agreed.
> >
> >-- 
> >~Ethan~
> I'm prepared to concede this point (as if my opinion as a very junior 
> member of the Python community counted for much :-) ).  Nick Coghlan and 
> Steven D'Aprano made a very strong case in their posts.
> My only real objection is that I would like consistency between "except" 
> statements and "except" expressions.

> But I suspect that you (plural), if you had the chance to rewrite 
> history, would also want to disallow a bare "except" statement. (Would you?)
> Nick, Steven, Ethan (and anybody else), are you willing to answer this 
> question?
> No offence intended, but I'm curious.  No, I should be honest: I'm 
> hoping to score a debating point.

No offence taken.

I think bare excepts are a bug magnet and violate "Explicit is better 
than implicit", and I would like to see them gone, even though they do 
have a use at the interactive interpreter for lazy people. Including me.

 py> try: this()
 ... except: None


Yes, I sometimes use that sort of quick-and-dirty construction, but if 
the language didn't have it, I wouldn't mind writing Exception after the 
except. Well, maybe a tiny bit. But not enough to complain.

I think bare excepts were useful back in ancient days when you 
could raise strings, and they were caught by identity not value. But I 
think there is strong evidence that this was a mistake: raising strings 
was removed in Python 2.6, rather than waiting for Python 3000. I expect 
that most people don't even remember that you ever could write things 
like 

    raise "This is an error"

and thank goodness for that :-)


-- 
Steven