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Groups > comp.lang.python > #67154
| From | Marko Rauhamaa <marko@pacujo.net> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Tuples and immutability |
| Date | 2014-02-27 18:19 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <87a9dczfya.fsf@elektro.pacujo.net> (permalink) |
| References | <lennh4$kpm$1@cabale.usenet-fr.net> |
Eric Jacoboni <eric.jacoboni@gmail.com>:
>>>> a_tuple[1] += [20]
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> TypeError: 'tuple' object does not support item assignment
>
> [...]
>
> But, then, why a_tuple is still modified?
That's because the += operator
1. modifies the list object in place
2. tries to replace the tuple slot with the list (even though the list
hasn't changed)
It's Step 2 that raises the exception, but the damage has been done
already.
One may ask why the += operator modifies the list instead of creating a
new object. That's just how it is with lists.
BTW, try:
>>> a_tuple[1].append(20)
>>> a_tuple[1].extend([20])
Try also:
>>> a_tuple[1] = a_tuple[1]
Marko
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Tuples and immutability Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-02-27 17:01 +0100
Re: Tuples and immutability Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-02-27 10:13 -0600
Re: Tuples and immutability Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-02-27 17:27 +0100
Re: Tuples and immutability Chris Angelico <rosuav@gmail.com> - 2014-02-28 03:33 +1100
Re: Tuples and immutability Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-02-27 10:47 -0600
Re: Tuples and immutability Nick Timkovich <prometheus235@gmail.com> - 2014-02-27 15:47 -0600
Re: Tuples and immutability Chris Angelico <rosuav@gmail.com> - 2014-02-28 08:52 +1100
Re: Tuples and immutability Ian Kelly <ian.g.kelly@gmail.com> - 2014-02-27 15:18 -0700
Re: Tuples and immutability Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2014-03-01 18:55 +0000
Re: Tuples and immutability Chris Angelico <rosuav@gmail.com> - 2014-02-28 03:14 +1100
Re: Tuples and immutability Marko Rauhamaa <marko@pacujo.net> - 2014-02-27 18:19 +0200
Re: Tuples and immutability John O'Hagan <research@johnohagan.com> - 2014-02-28 16:17 +1100
Re: Tuples and immutability Marko Rauhamaa <marko@pacujo.net> - 2014-02-28 09:54 +0200
Re: Tuples and immutability Joshua Landau <joshua@landau.ws> - 2014-02-28 14:41 +0000
Re: Tuples and immutability Chris Angelico <rosuav@gmail.com> - 2014-03-01 01:43 +1100
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-02-28 16:22 -0800
Re: Tuples and immutability Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-03-01 02:27 +0100
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-02-28 20:45 -0800
Re: Tuples and immutability Ian Kelly <ian.g.kelly@gmail.com> - 2014-02-28 22:34 -0700
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-02-28 21:50 -0800
Re: Tuples and immutability Ned Batchelder <ned@nedbatchelder.com> - 2014-03-01 12:56 -0500
Re: Tuples and immutability Ian Kelly <ian.g.kelly@gmail.com> - 2014-02-28 22:26 -0700
Re: Tuples and immutability Chris Angelico <rosuav@gmail.com> - 2014-03-01 12:39 +1100
Re: Tuples and immutability Ian Kelly <ian.g.kelly@gmail.com> - 2014-02-28 22:16 -0700
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-02-28 22:16 -0800
Re: Tuples and immutability Chris Angelico <rosuav@gmail.com> - 2014-03-01 17:29 +1100
Re: Tuples and immutability Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-01 14:54 +0000
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-03-01 13:01 -0800
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-02-28 22:25 -0800
Re: Tuples and immutability Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-01 12:45 -0700
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-03-01 13:21 -0800
Re: Tuples and immutability Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-03-02 03:04 +0100
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-03-01 18:28 -0800
Re: Tuples and immutability Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-02 05:32 -0700
Re: Tuples and immutability Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-03-02 14:38 +0100
Re: Tuples and immutability Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-02 14:05 +0000
Re: Tuples and immutability Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-03-02 15:17 +0100
Re: Tuples and immutability "albert visser" <albert.visser@gmail.com> - 2014-03-02 15:37 +0100
Re: Tuples and immutability "Mark H. Harris" <harrismh777@gmail.com> - 2014-03-01 18:15 -0800
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