Jim Jewett <jimjjewett@gmail.com> wrote:
I'll try to be more explicit; if Josiah and I are talking past each other, than the explanation was clearly not yet mature.
(In http://mail.python.org/pipermail/python-dev/2005-October/057251.html) Eyal Lotem suggested:
Name: Attribute access for all namespaces ...
global x ; x = 1 Replaced by: module.x = 1
I responded:
Attribute access as an option would be nice, but might be slower.
Also note that one common use for a __dict__ is that you don't know what keys are available; meeting this use case with attribute access would require some extra machinery, such as an iterator over attributes.
Josiah Carlson responded (http://mail.python.org/pipermail/python-dev/2005-October/057451.html)
This particular use case is easily handled. Put the following once at the top of the module...
module = __import__(__name__)
Then one can access (though perhaps not quickly) the module-level variables for that module. To access attributes, it is a quick scan through module.__dict__, dir(), or vars().
My understanding of the request was that all namespaces -- including those returned by globals() and locals() -- should be used with attribute access *instead* of __dict__ access.
Yeah, I missed the transition from arbitrary stack frame access to strictly global and local scope attribute access.
module.x is certainly nicer than module.__dict__['x']
Even with globals() and locals(), I usually *wish* I could use attribute access, to avoid creating a string when what I really want is a name.
Indeed.
The catch is that sometimes I don't know the names in advance, and have to iterate over the dict -- as you suggested. That works fine today; my question is what to do instead if __dict__ is unavailable.
Note that vars(obj) itself conceptually returns a NameSpace rather than a dict, so that isn't the answer.
help(vars) vars(...) vars([object]) -> dictionary
Without arguments, equivalent to locals(). With an argument, equivalent to object.__dict__. When an object lacks a dictionary, dir() works just fine.
help(dir) Help on built-in function dir:
dir(...) dir([object]) -> list of strings Return an alphabetized list of names comprising (some of) the attributes of the given object, and of attributes reachable from it: No argument: the names in the current scope. Module object: the module attributes. Type or class object: its attributes, and recursively the attributes of its bases. Otherwise: its attributes, its class's attributes, and recursively the attributes of its class's base classes.
My inclination is to add an __iterattr__ that returns (attribute name, attribute value) pairs, and to make this the default iterator for NameSpace objects.
def __iterattr__(obj): for i in dir(obj): yield i, getattr(obj, i)
Whether the good of (1) not needing to mess with __dict__, and (2) not needing to pretend that strings are names is enough to justify an extra magic method ... I'm not as sure.
I don't know, but leaning towards no; dir() works pretty well. Yeah, you have to use getattr(), but there are worse things. - Josiah