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Subject: Re: Design thought for callbacks
From: Cem Karan <cfkaran2@gmail.com>
In-Reply-To: <54EA43C8.2090309@stoneleaf.us>
Date: Sun, 22 Feb 2015 16:17:21 -0500
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To: Ethan Furman <ethan@stoneleaf.us>
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On Feb 22, 2015, at 4:02 PM, Ethan Furman <ethan@stoneleaf.us> wrote:

> On 02/22/2015 05:13 AM, Cem Karan wrote:
>=20
>> Output:
>> =46rom Evil Zombie: Surprise!
>> =46rom Your Significant Other: Surprise!
>>=20
>> In this case, the user made an error (just as Marko said in his =
earlier message),
>> and forgot about the callback he registered with the library.  The =
callback isn't
>> really rising from the dead; as you say, either its been garbage =
collected, or it
>> hasn't been.  However, you may not be ready for a callback to be =
called at that
>> moment in time, which means you're surprised by unexpected behavior.
>=20
> But the unexpected behavior is not a problem with Python, nor with =
your library -- it's a bug in the fellow-programmer's
> code, and you can't (or at least shouldn't) try to prevent those kinds =
of bugs from manifesting -- they'll just get
> bitten somewhere else by the same bug.

I agree with you, but until a relatively new programmer has gotten used =
to what callbacks are and what they imply, I want to make things easy.  =
For example, if the API subclasses collections.abc.MutableSet, and the =
documentation states that you can only add callbacks to this particular =
type of set, then a new programmer will naturally decide that either a) =
they need to dispose of the set, and if that isn't possible, then b) =
they need to delete their callback from the set.  It won't occur to them =
that their live object will just magically 'go away'; its a member of a =
set!

My goal is to make things as pythonic (whatever that means in this case) =
and obvious as possible.  Ideally, a novice can more or less guess what =
will happen with my API without really having to read the documentation =
on it. =20

Thanks,
Cem Karan=