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Subject: Re: Why no warnings when re-assigning builtin names?
From: Philip Semanchuk <philip@semanchuk.com>
In-Reply-To: <4E4A8F94.50706@stoneleaf.us>
Date: Tue, 16 Aug 2011 11:38:57 -0400
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On Aug 16, 2011, at 11:41 AM, Ethan Furman wrote:

> Philip Semanchuk wrote:
>> On Aug 16, 2011, at 1:15 AM, Steven D'Aprano wrote:
>>> Protecting n00bs from their own errors is an admirable aim, but have =
you
>>> considered that warnings for something which may be harmless could =
do more
>>> harm than good?
>> Isn't the whole point of a warning to highlight behavior that's not =
strictly
> > wrong but looks iffy? Sort of, "I can't be sure, but this looks like =
trouble
> > to me. I hope you know what you're doing". If we are to eschew =
warnings in
> > cases where they might be highlighting something harmless, then we =
would
> > have no warnings at all.
>=20
> Sounds good to me.  ;)  Keep such things in the IDE's, and then those =
who desire such behavior can have it there.  Do not clutter Python with =
such.

You wink, yet you sound serious. What's with the mixed message? Do you =
honestly advocate removing all warnings from Python, or not? I sincerely =
would like to know what you think.


>>> Perhaps. But I'm not so sure it is worth the cost of extra code to =
detect
>>> shadowing and raise a warning. After all, the average coder probably =
never
>>> shadows anything,
>> One need look no further than the standard library to see a strong
> > counterexample. grep through the Python source for " file =3D". I =
see dozens
>> of examples of this builtin being used as a common variable name. I =
would
> > call contributors to the standard library above-average coders, and =
we can
> > see them unintentionally shadowing builtins many times.
>=20
> What makes you think it's unintentional?  file makes a good variable =
name, and if you don't need it to actually open a file there's nothing =
wrong with using it yourself.

"Unintentional" as in, "I'm using file as a variable name because it's =
handy" as opposed to intentional as in "Yes, I am deliberately changing =
the meaning of this builtin".=20


>>> and for those that do, once they get bitten *once* they
>>> either never do it again or learn how to shadow safely.
>> I have done it plenty of times, never been bitten (thankfully) and =
still
> > do it by accident now and again.
>=20
> Seems to me the real issue is somebody using a builtin, such as str or =
int, and that they somehow manage to do this without realizing, "wait a =
sec', that's one of my variables!" =20

Yes


> I don't see that as a problem that Python needs to solve.

"need" is a strong word. Python will be fine regardless of whether this =
changes or not. I believe Python could be improved; that's all I'm =
arguing.

Cheers
Philip