[Python-ideas] Idea to support lazy loaded names.

[Steven D'Aprano]

On Mon, Oct 06, 2014 at 11:51:45PM -0400, Terry Reedy wrote:
> On 10/6/2014 11:30 PM, Steven D'Aprano wrote:
[...]
> >This is relevant because modules are instances, and module attributes
> >live in the instance __dict__.
> 
> So a 'solution' might be to make modules be instances (but with no 
> __new__ or __init__) of a module metaclass, so that module dicts could 
> act like class dicts with respect to descriptors.  I have no idea how 
> much code this would break ;-).

Probably lots :-)

It's not common to write something like this outside of a class:

x = property(some_function)

but if you did, you would normally expect lookups on x to return the 
property object itself, not call the __get__ method. That's what happens 
now, and so by backward compatibility that can't change.

More importantly, defining top-level functions is ubiquitous in Python 
code. And functions obey the descriptor protocol! That's how functions 
magically turn into methods when put inside a class. So if modules 
called __get__ by default, every single function lookup would break. 
That would be bad.

So any change to the behaviour of module lookups would need to be 
opt-in.


-- 
Steven