[Python-ideas] a simple namespace type

[Calvin Spealman]

On Sat, May 26, 2012 at 2:53 PM, Eric Snow <ericsnowcurrently at gmail.com> wrote:
> On Thu, May 24, 2012 at 1:34 PM, Eric Snow <ericsnowcurrently at gmail.com> wrote:
>> On Thu, May 24, 2012 at 12:14 PM, Guido van Rossum <guido at python.org> wrote:
>>> On Thu, May 24, 2012 at 10:17 AM, Eric Snow <ericsnowcurrently at gmail.com> wrote:
>>>>  Effectively this is just a simple but distinct facade around dict to
>>>> give a namespace with attribute access.  I suppose part of the
>>>> question is how much of the Mapping interface would belong instead to
>>>> a hypothetical Namespace interface. (I'm definitely _not_ proposing
>>>> such an unnecessary extra level of abstraction).
>>>
>>> Possibly there is a (weird?) parallel with namedtuple. The end result
>>> is somewhat similar: you get to use attribute names instead of the
>>> accessor syntax (x[y]) of the underlying type. But the "feel" of the
>>> type is different, and inherits more of the underlying type
>>> (namedtuple is immutable and has a fixed set of keys, whereas the type
>>> proposed here is mutable and allows arbitrary keys as long as they
>>> look like Python names).
>>
>> Yeah, the feel is definitely different.  I've been thinking about this
>> because of the code for sys.implementation.  Using a structseq would
>> probably been the simplest approach there, but a named tuple doesn't
>> feel right.  In contrast, a SimpleNamespace would fit much better.
>>
>> As far as this goes generally, the pattern of a simple, dynamic
>> attribute-based namespace has been implemented a zillion times (and
>> it's easy to do).  This is because people find a simple dynamic
>> namespace really handy and they want the attribute-access interface
>> rather than a mapping.
>>
>> In contrast, a namedtuple is, as Nick said, "the standard library's
>> answer for structured records".  It's an immutable (attribute-based)
>> namespace implementing the Sequence interface.  It's a tuple and
>> directly reflects the underlying concept of tuples in Python by giving
>> the values names.
>>
>> SimpleNamespace (and the like) isn't a structured record.  It's only
>> job is to be an attribute-based namespace with as simple an interface
>> as possible.
>>
>> So why isn't a type like SimpleNamespace in the stdlib? Because it's
>> trivial to implement.  There's a certain trivial-ness threshold a
>> function/type must pass before it gets canonized, and rightly so.
>>
>> Anyway, while many would use something like SimpleNamespace out the
>> the standard library, my impetus was having it as a builtin type so I
>> could use it for sys.implementation.  :)
>>
>> FWIW, I have an implementation (pure Python + c extension) of
>> SimpleNamespace on PyPI:
>>
>>  http://pypi.python.org/pypi/simple_namespace
>>
>> -eric
>
> Any further thoughts on this?  Unless anyone is strongly opposed, I'd
> like to push this forward.

There is no good name for such a type. "Namespace" is a bad name, because
the term "namespace" is already a general term that describes a lot of things in
Python (and outside it) and shouldn't share a name with a specific
thing, this type.
That this specific type would also be within the more general namespace-concept
only makes that worse.

So, what do you call it?

Also, is this here because you don't like typing the square brackets
and quotes? If
so, does it only save you three characters and is that worth the increase to the
language size?

A final complaint against: would the existence of this fragment
python-learners education
to the point that they would defer learning and practicing to use
classes properly?

Sorry to complain, but someone needs to in python-ideas! ;-)
Calvin

> -eric
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