A class for C-like structuures in Python

[Donn Cave]

Quoth Thomas Gagne <tgagne at ix.netcom.com>:
| I don't think I should be using __dict__, __getattr() and __setattr().  The
| problem is it seems to internalize the member list as though they were fields
| inside the structure.  This could be fine except that a) I can't get it
| working (see previous message) and b) what if the variables defined conflict
| with variables that are part of the class hierarchy?  Suppose someone wanted
| to name a variable __str__ for whatever reason, this could be bad in Python.
| But holding a dictionary entry for "__str__" wouldn't.
|
| Having to code IsdHeader.valueFor('len') instead of the shorter IsdHeader.len
| may be a tad awkward, but it should work in all circumstances, no?

I don't like __get/setattr__ a lot, but advantages come to mind:

1.  There is no API, so
  a) not a tad awkward, and
  b) can be installed when necessary, only after it's clear they're needed.
2.  Performance costs of accessors could be non-trivial, and with a
    combination of __getattr__ and __dict__ you can get some lookups
    free if the attributes are, at your discretion, defined directly
    in __dict__.

All of this reflects the point of view that accessor functions aren't
standard operating procedure in Python.  I can't speak for anyone but
myself, but that's my bias, I think they're usually out of place.  The
motive is good, but we get better return on time invested in higher
level functionality.

	Donn Cave, donn at u.washington.edu