Correct use of try,except and raise?

[Ben Finney]

Roy Smith <roy at panix.com> writes:

> Ben Finney <bignose+hates-spam at benfinney.id.au> wrote:
> 
> > If you are passing a sequence conceptually, then it's more Pythonic to
> > pass it as a sequence explicitly::
> > 
> >     def __init__(self, items):
> >         """ Call with e.g. Stack(["foo", "bar"]) """
> >         self.stack = list(items)
> 
> I don't get this. You're forcing a copy to be made of the list.

The 'items' object might not be a list; it might be some other
sequence. The rest of the class (as shown by the original poster)
requires it to be a list.

> This changes the semantics of the original class, because the
> operations no longer change the original list.

Which "original class" are you referring to? The one posted by the
original poster of this thread had no "original list"; it gathered the
positional arguments (using '*items') into an 'items' parameter, which
*doesn't exist* until the function body executes.

There *is* no "original list" in that implementation posed by the
original poster; it's constructed at call time from the positional
parameters to the function.

If anything, my implementation above *preserves* that semantic, by
making a new list from the passed-in sequence.

-- 
 \        “Consider the daffodil. And while you're doing that, I'll be |
  `\              over here, looking through your stuff.” —Jack Handey |
_o__)                                                                  |
Ben Finney