A Suggestion for Python Dictionary/Class

[Donn Cave]

Quoth William Djaja Tjokroaminata <billtj at y.glue.umd.edu>:
...
| Therefore, is there any way for me to define a class, with some definite
| members just like in C/C++/Java, so that no new members can be defined?  I
| am trying to do it, but using some conventions, not using the Python
| language features.
|
| Because Python provides a read-only list in terms of tuple, I think it
| will be nice if Python provides another class type with fixed members,
| just like a dictionary with read-only keys.  Any opinion, anyone?

When you say "using some conventions, not using the Python language
features", do you mean to reject a solution like this?

    class Fixed:
        def fixdict(self):
            for a in self.fixed_attributes:
                self.__dict__[a] = None
        def __setattr__(self, a, v):
            if self.__dict__.has_key(a):
                self.__dict__[a] = v
            else:
                raise AttributeError, a

    class Plant(Fixed):
        fixed_attributes = ('flower', 'stem', 'root', 'leaf')
        def __init__(self, n):
            self.fixdict()
            self.root = n

    p = Plant(5)
    print p.root
    print p.stem

I hope that will work for you, because it seems to provide the
behavior you describe and it works already, with no changes to
Python.

	Donn Cave, donn at u.washington.edu