[Tutor] Why use main() ?

[Mats Wichmann]

On 07/05/2017 09:45 AM, Zachary Ware wrote:
> On Wed, Jul 5, 2017 at 10:37 AM, David Rock <david.rock at gmail.com> wrote:

>> I personally find using main() cumbersome, but many examples I come
>> across use main().  Is there some fundamental benefit to using main()
>> that I'm missing?
> 
> In no particular order: testing, encapsulation, and reusability.  With
> a "main()" function (which, recall, can be named whatever you like; it
> doesn't have to be "main") you can directly call the function in your
> tests to make sure it acts the way you want.  The encapsulation of the
> "main" code in a "main()" function also reduces your global state (and
> makes global state a bit more difficult to use), which is usually a
> good thing.  And finally, it makes it possible to use the "main()"
> function in some other piece of code that imports it.
> 

As a vaguely contradictory position to a part of this (which I in the
main agree with): if your objective is to make a module, and also have
some code (perhaps including test code) which is run in the non-module
(aka not-imported) case, then stuffing that code in a function main()
means you've exposed that not-really-module-code as part of the module,
and might then want to take steps to hide it from clients so it doesn't
end up looking like part of the module API.