[Python-ideas] Object grabbing

[Steven D'Aprano]

On Sun, May 01, 2016 at 09:25:17PM -0400, Random832 wrote:

> Is there any reason not to simply implement a performance optimization
> for the normal syntax?

Yes. You can't assume that myobject is the same object in both 
statements. A silly toy example:

class MyObject:
    def deactivate(self):
        global myobject
        myobject = None
    def fire(self):
        launch_missiles()

myobject.deactivate()
myobject.fire()

A more realistic case would be if you have a mutable object:

myobject[1].lookup['key'].property.a()
myobject[1].lookup['key'].property.b()

The compiler cannot assume that (myobject[1].lookup['key'].property) 
will refer to the same thing in the two calls. But the programmer can 
explicitly do so, using either a temporary variable, or the proposed 
"using" statement.


-- 
Steve