stefan <topjet...@yahoo.com> added the comment:
Thank you for your reply and the lucid explanation.
On Monday, May 20, 2019, 9:15:42 PM EDT, Steven D'Aprano
<rep...@bugs.python.org> wrote:
Steven D'Aprano <steve+pyt...@pearwood.info> added the comment:
Hi Stefan, and welcome.
This is not a help desk, you really should ask elsewhere for explanations of
how Python works. There are no bugs here: what you are seeing is standard
pass-by-object behaviour.
You are misinterpreting what you are seeing. Python is never pass by reference
or pass by value.
https://en.wikipedia.org/wiki/Evaluation_strategy
https://www.effbot.org/zone/call-by-object.htm
*All* function objects, whether strings, ints, lists or numpy arrays, are
passed as objects. If you want to make a copy, you have to explicitly make a
copy. If you don't, and you mutate the object in place, you will see the
mutation in both places.
> Shouldn't the id of each variable be different if they are different
> instances?
Not necessarily: IDs can be reused. Without seeing the actual running code, I
can't tell if the IDs have been used or if they are the same ID because they
are the same object.
> Would it possible for the python interpreter/compiler to let me know when a
> function is going to clobber a variable that is not used in the function or
> passed to the function or returned by the function
Python never clobbers a variable not used in the function. It may however
mutate an object which is accessible from both inside and outside a function.
----------
nosy: +steven.daprano
resolution: -> not a bug
stage: -> resolved
status: open -> closed
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue36980>
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue36980>
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