for convenience

[Paul St George]

On 21/03/2022 18.04, dn wrote:

> On 22/03/2022 10.17, Chris Angelico wrote:
> > On Tue, 22 Mar 2022 at 08:13, Paul St George <email at paulstgeorge.com <https://mail.python.org/mailman/listinfo/python-list>> wrote:
> >>
> >>
> >> When I am writing code, I often do things like this:
> >>
> >> context = bpy.context  # convenience
> >>
> >> then whenever I need bpy.context, I only need to write context
> >>
> >>
> >> Here’s my question:
> >>
> >> When I forget to use the convenient shorter form
> >>
> >> why is bpy.context not interpreted as bpy.bpy.context?
> >>
> > 
> > I don't understand the question. When you do that "for convenience"
> > assignment, what you're doing is creating a local variable named
> > "context" which refers to the same thing that bpy.context does (or did
> > at the time of the assignment, but presumably you only do this when
> > bpy.context won't get reassigned). It has no effect on any other name.
> > There's no magic happening here - it's just assignment to the name
> > context, like anything else.
> > 
> > What are you expecting to happen here?
> 
> 
> It's the way Python works.
> 
> try:
> 
> context = bpy.context  # convenience
> print( id(context), id(bpy.context) )
> 
> Remember that the 'relationship' between the two is established at
> run-time and at the data/address 'level' - and not at compile-time. Thus
> "context" points to a memory location, and does not 'stand for'
> "bpy.context" anywhere other than in your mind.
> 
> (which is why we often need to use a copy() when we want 'separate data'
> - see also the 'counters' Python uses to manage "garbage collection")
> 
> -- 
> Regards,
> =dn


Thanks dn,
I did exactly as you suggested.

import bpy

context = bpy.context  # convenience variable
print( id(context), id(bpy.context) )

4932508928 4932508928

The two are the same, and that makes it crystal clear. And, as a bonus you have explained a use of copy().

—
Thanks,
Paul