PyMyth: Global variables are evil... WRONG!

[Joel Goldstick]

On Thu, Nov 14, 2013 at 12:26 PM, Rick Johnson
<rantingrickjohnson at gmail.com> wrote:
> On Wednesday, November 13, 2013 11:50:40 PM UTC-6, Steven D'Aprano wrote:
>> On Wed, 13 Nov 2013 19:45:42 -0800, Rick Johnson wrote:
>> > On Wednesday, November 13, 2013 8:45:16 PM UTC-6, Steven D'Aprano wrote:
>> >>  A fully-auto machine gun with a hair-trigger and no
>> >> safety is no  different from a single-barrel shotgun with a safety and
>> >> a trigger lock!  You can blow your foot off with both!
>> > Yes. But in the case of the shotgun you'd have to find the key, unlock
>> > the trigger, unset the safety, and aim REALLY well... because your only
>> > getting off one shot, and if you miss or only wound me, i've got that
>> > full auto machine gun with hair trigger and no safety -- i won't need to
>> > live very long to return the favor. >:)
>> I think you're missing the point that we're talking about the coder
>> shooting themselves in the foot, not Gunfight At The OK Corral. There's
>> no "favour" to return.
>
> And you missed the point that i took your straw-man and
> converted him into satire. You owe me gratitude for
> *politely* ignoring your repeated logical fallacies.
>
>> Yes, the point is that process-wide global variables are
>> demonstrated by 50+ years of programming experience to be
>> best avoided (in general -- there are caveats and
>> exceptions of course). We're talking about probably
>> millions of person-hours of experience leading to the
>> conclusion that "globals are harmful".
>
> But yet Python has globals, you just have to *import* them.
> But that design is flawed
>
>> It isn't that global variables will leap out of the
>> computer and attack you while you sleep,
>
> Funny, that sounds like my argument from earlier. Something
> about "gremlins".
>
>> of course, but that in general *its too damn hard* for
>> human programmers to write good, reliable, maintainable,
>> correct (i.e. bug-free) code using process-wide global
>> variables.
>
> Complete FUD. Maybe for you. Not for me.
>
>> Global variables are the spaghetti code of namespacing --
>> everything is mixed up together in one big tangled mess.
>
> It's a tangled mess if you design it to be a tangled mess.
>
>> The more global variables you have, the worse the tangle.
>
> Complete illogic.
>
> What if all the globals are only accessed
> and never mutated? You could have a million globals that never
> change (of course they'd technically be constants) and never
> suffer a single error from globals EVEN IF your an incompetent
> software designer.
>
>> One or two is not too bad. With good conventions for
>> encapsulation to limit the amount of tangled, coupled code
>> (e.g. naming conventions, or limiting globals to a single
>> module at a time by default) the amount of harm can be
>> reduced to manageable levels.
>
>> SO now your agreeing that globals are not evil again. I
>> positied an anaology in a passed thred that went something
>> like this:
>
> ManufacurerA claims his car is the safest on the road.
>
> ManfacturerB drives ManfacturerA's car into a ditch and then
> claims ManfacturerA is a liar.
>
> Result: Who is wrong?
>
>> Global variables increases coupling between distant parts
>> of the code. I remember a nasty little bug in Windows
>> where removing IE stopped copy-and- paste from working
>> everywhere. That's a sign of excess coupling between code
>> -- there's no logical reason why removing a web browser
>> should cause copying text in Notepad to fail.
>
> Do you have link describing this bug? I am not aware of such
> bug ,but uh, i would not at all be surprised that windows
> could break from removing that gawd awful IE.
>
> Come to think of it, i'll bet it's not even a bug at all,
> but a feature to prevent "wise users" from removing IE,
> thereby maintaining IE's footprint in the wild.
>
> Steven, this sounds more like Fascism than "clumsy use of
> globals" to me.
>
> But even IF globals are to blame, by removing IE, you have
> removed a large chunk of code from a code base that was not
> designed for modularity. (We could argue whether or not
> windows should allow removal of IE, but ultimately that is
> M$ decision)
>
> No developer could possibly forecast every possible "bad
> thing" a user might decide to do. Especially when we're
> talking about ripping components of the software out
> completely.
>
> Do i think IE should be a removal component? HECK YEAH, and
> i would have designed it that way. But IS is not my baby, it
> belongs to Mr. Gates, and he designs his software any way he
> damn well pleases, and you and i can choose not to use it.
>
> Image if someone downloaded Python and just started ripping
> out source files willy-nilly because they did not like them
> for whatever reason. Then, they came to this list and start
> bitching because Python was blowing chunks. And don't give
> examples of things that can be ripped out without breaking
> Python, because that is germane either.
>
> How would you respond to such complaints?
>
> Hmm...never thought you'd be agree with Mr. Gates did ya?
>
>> We want to avoid unnecessary coupling: opening your fridge
>> door shouldn't flush the toilet.
>
> *KAH-BOOM* (Straw-bomb expodes)(AGAIN!)
>
>> Since global variables increase coupling, and coupling is
>> often harmful, one way to avoid unnecessary coupling is to
>> avoid unnecessary global variables.
>
> Nice! Your attempts to posit that "harmful coupling" is the
> almost unavoidable outcome of "globals" is not fooling me.
> Here's another way to phrase:
>
>     Since transportation increases chances of death or
>     injury from accidents, and death or injury is often
>     harmful, one way to to avoid unnecessary death or injury
>     is to avoid transportation.
>
> There are two logical ways to react to such grim reality:
>
>     We could become consumed with fear and destroy all motor
>     vehicles, bicycles, skateboards, etc...  and instead
>     adopt the locomotion of our forefathers by utilizing our
>     feet. or,
>
>     We reduce the risks to almost nothing by designing and
>     implementing globals via a logical and consistent
>     interface. Then, to be sure, we test religiously
>     (psst:we should be doing this anyway!!!)
>
> But what we don't want to do is lull ourselves into a false
> sense of security by "hiding" globals behind a pseudo
> interface and thinking we have solved the problem of
> globals.
>
> And this is what Python modules are doing!
>
> No, you've solved nothing. All you've done is to
> stick you head in the sand.
>
> ============================================================
>  It's my code, my problem, not yours!
> ============================================================
>
> Yes, you are correct.
>
> If you want to go on using globals in a dangerous way, or
> using module attributes and believing falsely they're not
> global, then by all means go on. HOWEVER, don't infect the
> world with your sloppy architecture. KEEP YOU CODE TO
> YOURSELF!
>
> But that's not the case is it, NO, many of you are infecting
> Python's code base with horrible code.
>
> Python's warts are *really* exposed when Python is embedded
> as a scripting language. Since multiple scripts from
> multiple authors will be running under the same process, any
> one of them can bring the whole house of cards crashing
> down. And with Python's current design, that possibility is
> more likely.
>
> It's sad, because Python is a great choice for scripting,
> but the major design flaws are self defeating. Even
> the best syntax ever created cannot make up for such
> illogical inconsistencies at the core.
>
>> Think of them as leaches. [snip remaining straw-bombs]
> --
> https://mail.python.org/mailman/listinfo/python-list

I've been following along this thread a little bit.  From what I get
out of it that the OP thinks only lousy coders can't write good code
with globals. If you are skilled (as he claims) they are useful.  The
con argument says that over 50 years of learning how to make better
more productive computer languages, globals end up causing certain
problems.

So, beyond that, what is the point of the thread?  Is it about python?
 Just barely I guess

-- 
Joel Goldstick
http://joelgoldstick.com