How to make a variable's late binding crosses the module boundary?

[Richard Damon]

On 8/27/22 7:42 AM, Mark Bourne wrote:
> Jach Feng wrote:
>> I have two files: test.py and test2.py
>> --test.py--
>> x = 2
>> def foo():
>>      print(x)
>> foo()
>>
>> x = 3
>> foo()
>>
>> --test2.py--
>> from test import *
>> x = 4
>> foo()
>>
>> -----
>> Run test.py under Winows8.1, I get the expected result:
>> e:\MyDocument>py test.py
>> 2
>> 3
>>
>> But when run test2.py, the result is not my expected 2,3,4:-(
>> e:\MyDocument>py test2.py
>> 2
>> 3
>> 3
>>
>> What to do?
>
> `from test import *` does not link the names in `test2` to those in 
> `test`.  It just binds objects bound to names in `test` to the same 
> names in `test2`.  A bit like doing:
>
> import test
> x = test.x
> foo = test.foo
> del test
>
> Subsequently assigning a different object to `x` in one module does 
> not affect the object assigned to `x` in the other module. So `x = 4` 
> in `test2.py` does not affect the object assigned to `x` in `test.py` 
> - that's still `3`.  If you want to do that, you need to import `test` 
> and assign to `test.x`, for example:
>
> import test
> test.x = 4
> test.foo()
>
Yes, fundamental issue is that the statement

from x import y

makes a binding in this module to the object CURRECTLY bound to x.y to 
the name y, but if x.y gets rebound, this module does not track the changes.

You can mutate the object x.y and see the changes, but not rebind it.

If you need to see rebindings, you can't use the "from x import y" form, 
or at a minimum do it as:


import x

from x import y

then later to get rebindings to x.y do a

y = x.y

to rebind to the current x.y object.

-- 
Richard Damon