On 10/16/17 9:06 PM, bartc wrote:
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.
Steve meant that syntactically it had to be valid on the left-hand
side. "x" is a syntactically valid LHS, "1+1" is not.
--Ned.
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