why del is not a function or method?

[bartc]

On 17/10/2017 01:53, Steve D'Aprano wrote:
> On Tue, 17 Oct 2017 03:16 am, Oren Ben-Kiki wrote:
> 
>> That doesn't explain why `del` isn't a method though.
> 
> 
> `del` cannot be a method or a function, because the argument to `del` is the
> name of the variable, not the contents of the variable.
> 
> If we write:
> 
>      x = 123
>      del x
> 
> then `del` needs to delete the *name* "x", not the value of x, namely 123. If
> del were a function or method, it would only see the value, 123, and have no
> idea what the name is.
> 
> `del` is kind of like an "anti-assignment" in that the argument to `del` must
> be exactly the same sort of expression that can appear on the left hand side
> of assignment:
> 
> 
>      123 = 1+1  # illegal
>      del 123  # also illegal

Yet in Stefan Ram's example with del applied to a local 'x', it raised 
an error on:

     del x        # x not yet assigned to

but an assignment to x would have been fine.