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Date: Sun, 3 Aug 2014 02:17:44 -0700
From: Albert-Jan Roskam <fomcl@yahoo.com>
Subject: Re: Correct type for a simple "bag of attributes" namespace object
To: Terry Reedy <tjreedy@udel.edu>, "python-list@python.org" <python-list@python.org>
In-Reply-To: <lrk7li$6nb$1@ger.gmane.org>
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Xref: csiph.com comp.lang.python:75583

--- Original Message -----=0A> From: Terry Reedy <tjreedy@udel.edu>=0A> To:=
 python-list@python.org=0A> Cc: =0A> Sent: Sunday, August 3, 2014 4:43 AM=
=0A> Subject: Re: Correct type for a simple "bag of attributes" namespace o=
bject=0A> =0A> On 8/2/2014 8:59 PM, Ian Kelly wrote:=0A>>  On Sat, Aug 2, 2=
014 at 2:46 PM, Mark Summerfield =0A> <list@qtrac.plus.com> wrote:=0A>>>  O=
n Saturday, 2 August 2014 20:58:59 UTC+1, Ben Finney=A0 wrote:=0A>>>>  Stev=
en D'Aprano writes:=0A>>>> =0A>>>>>  If you need instances which carry stat=
e, then object is the =0A> wrong=0A>>>>>  class.=0A>>> =0A>>>  Fair enough.=
=0A>>> =0A>>>>  Right. The 'types' module provides a SimpleNamespace class =
=0A> for the=0A>>>>  common "bag of attributes" use case::=0A>>>> =0A>>>> =
=A0 =A0 =A0 >>> import types=0A>>>> =A0 =A0 =A0 >>> foo =3D types.SimpleNam=
espace()=0A>>>> =A0 =A0 =A0 >>> foo.x =3D 3=0A>>>> =A0 =A0 =A0 >>> foo=0A>>=
>> =A0 =A0 =A0 namespace(x=3D3)=0A>>> =0A>>>  This is too much for children=
 (& beginners).=0A>>> =0A>>>  But perhaps what I should be asking for is fo=
r a new built-in that does =0A> what types.SimpleNamespace() does, so that =
without any import you can write, =0A> say,=0A>>> =0A>>>  foo =3D namespace=
(a=3D1, b=3D2)=0A>>>  # or=0A>>>  bar =3D namespace()=0A>>>  bar.a =3D 1=0A=
=0AI find the following obscure (to me at least) use of type() useful exact=
ly for this "bag of attributes" use case:=0A>>> employee =3D type("Employee=
", (object,), {})=0A>>> employee.name =3D "John Doe"=0A>>> employee.positio=
n =3D "Python programmer"=0A>>> employee.name, employee.position, employee=
=0A('John Doe', 'Python programmer', <class '__main__.Employee'>)=0A=0A>>> =
details =3D dict(name=3D"John Doe", position=3D"Python programmer")=0A>>> e=
mployee =3D type("Employee", (object,), details)=0A>>> employee.name, emplo=
yee.position, employee=0A('John Doe', 'Python programmer', <class '__main__=
.Employee'>)=0A=0A=0Aregards,=0AAlbert-Jan =0A