On Aug 20, 2009, at 11:07 PM, josef wrote:
To begin, I'm new with python. I've read a few discussions about
object references and I think I understand them.
To be clear, Python uses a "Pass By Object Reference" model.
x = 1
x becomes the object reference, while an object is created with the
type 'int', value 1, and identifier (id(x)). Doing this with a class,
x = myclass(), does the same thing, but with more or less object
attributes. Every object has a type and an identifier (id()),
according to the Python Language Reference for 2.6.2 section 3.1.
x in both cases is the object reference. I would like to use the
object to refer to the object reference.
Stop right there. 'x' is not *the* object reference. It is *an*
object reference (or in my preferred terminology, a label). Suppose
you do:
x = myclass()
y = x
The labels 'x' and 'y' both refer to the same object with equal
precedence. There is no mapping from object back to label; it is a
one-way pointer. Also importantly, labels themselves are not objects,
and cannot be accessed or referred to.
(This is a slight oversimplification; thanks to Python's reflection
and introspection capabilities, it is possible to access labels to
some extent, and in some limited situations it is possible to use
stack inspection to obtain a label for an object. But this is hackish
and error-prone, and should never be used when a more Pythonic method
is available.)
The following is what I would like to do:
I have a list of class instances dk = [ a, b, c, d ], where a, b, c, d
is an object reference. Entering dk gives me the object: [MyClass0
instance at 0x0000, MyClass1 instance at 0x0008, MyClass2 instance at
0x0010 ... ]
I need the object reference name (a,b,c,d) from dk to use as input for
a file.
It sounds like you should either be storing that name as an attribute
of the object, or using a dictionary ({'a': a, 'b': b, ...}).
-Miles
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