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.
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