Are decorators really that different from metaclasses...
pm_mon at yahoo.com
Sat Aug 28 00:39:51 CEST 2004
Anthony Baxter wrote:
> On Thu, 26 Aug 2004 16:09:42 -0400, Paul Morrow <pm_mon at yahoo.com> wrote:
>>Yes, it doesn't seem all that complex, although I'm not sure that
>>everyone reading this understands them and their subtleties. The
>>following is an excerpt from
>>"A namespace is a mapping from names to objects. Most namespaces are
>>currently implemented as Python dictionaries, but that's normally not
>>noticeable in any way (except for performance), and it may change in the
>>future. Examples of namespaces are: the set of built-in names (functions
>>such as abs(), and built-in exception names); the global names in a
>>module; and the local names in a function invocation. In a sense the set
>>of attributes of an object also form a namespace."
>>When I talk about namespaces, I include all of the above, including the
>>sense mentioned in the last line. So an object's attributes constitute
>>a namespace too. Therefore __doc__, being an attribute of the function
>>object, is in the function object's /namespace/. And note that this is
>>*not* a new namespace; it's been there all along.
> "In a sense" is the bit you're missing here. You can't just hand-wave
> and say that it's a namespace. It's *not* a namespace. If it was, you
> could do any of these:
No I didn't miss it (I read that bit). In a sense, every object has
it's own namespace. So that means that every class, every module, every
function has a namespace (in a sense). The namespace (the mapping from
names to objects) is stored in each object's special __dict__ attribute.
Ok, and this is certainly apparent with classes.
>>> class Foo:
... """docstring for Foo"""
'docstring for Foo'
And because of the parallels between the above class definition of Foo
and the following function definition of baz, I would expect the same
>>> def baz():
... """docstring of baz"""
'docstring of baz'
Say what? Why didn't the Python system put baz's docstring into it's
namespace (__dict__)? And where did it put it?
I would like to understand the answers to these questions. Can you
answer them (will you)? If not, can you please point me at something
that documents what's going on here?
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