encapsulating a global variable

[BlindAnagram]

On 25/02/2020 14:13, Chris Angelico wrote:
> On Wed, Feb 26, 2020 at 12:11 AM BlindAnagram <blindanagram at nowhere.com> wrote:
>>
>> On 25/02/2020 12:56, Chris Angelico wrote:
>>> On Tue, Feb 25, 2020 at 11:41 PM BlindAnagram <blindanagram at nowhere.com> wrote:
>>>>
>>>> I would appreciate advice on whether it is possible to avoid the use of
>>>> a global variable used in a function by encapsulating it in a class
>>>> without maaking any changes to the call interface (which I cannot change).
>>>
>>> Why bother? If you aren't changing where the function's called, then
>>> its state is effectively global anyway, so what's the point of the
>>> class?
>>
>> It's a good question!
>>
>> The main reason is that I would like to know if it is possible as I then
>> have a choice.  The choice might not be there.
>>
> 
> Well, yes, you can, but you would need a global instance of that class
> (or use the global class object itself). So you'd still have a global.
> 
> But if this is a transitional thing, then the answer is a resounding
> YES. You can start by packaging up all your state with a class, and
> have a single global instance of that class; but then you can rework
> your function to take an optional parameter which is a non-global
> instance of the class. Then all your state is kept in there, and you
> actually truly *do* avoid global state. As a good example of how this
> works, check out Python's random module - you can call
> random.randrange() to get a random number in a particular range, or
> you can instantiate your own random.Random() object and call its
> randrange() method. The first form uses global state; the second form
> doesn't.

Thanks, I think I understand most of this but the eample will help a lot.

My interest in this stems from wanting to keep the dictionary only
available to the function that uses it and also a worry about being
called from threaded code.

   Brian