[Tutor] Fixing Globals

[kendy at kendy.org]

Thanks to everyone who responded. I learned from each person's response.

The example code that I emailed was representative of many large programs that
I've written in other languages. I've written many small Python scripts and I'm
about to write a more complex Python script, much like the example -- needing
help with globals. Thanks for your help!!!

Alan's response was particularly interesting.

On Sat Mar 16 16:07 , Alan Gauld  sent:

>On 16/03/13 19:04, kendy at kendy.org wrote:
>
>> Global constants and variables are bad.
>
>Really? Do you know why?
>If you understand why then the measures to avoid them
>become more palatable - the lesser of 2 evils.
>
>Read-only globals are much less of a problem than read/write ones.
>And in Python we limit the damage by restricting globals to a single 
>module's scope. class variables do a similar job in OOP.

Why are they bad? Hmmm. Because people say so? Hmmm. It's best to restrict
dependencies. It's not fun to change one thing that affects many, far-away places.

I actually don't mind globals if they're done well. I think passing a long list
of arguments is the worst -- it becomes a big management issue and it clutters.
Better programming helps minimize globals and long argument lists, but I don't
see how they can always be eliminated.

Books and teachers usually don't go into much detail about globals. I think that
this is an important topic and I want to learn more. I now have more confidence
but don't have a total grasp.

Best regards,
Ken