building embedded classes as in C/C++

Andy Beall beall at psych.ucsb.edu
Wed Aug 4 02:12:41 CEST 1999


Hi,

I'd like to build an embedded structure (Python class) much like I do in
C if possible.  When I do the following, multiple instances of my final
class overwrite each others sub-class values!

-------------------------------------------------------------------------
class Point:
	x = 0
	y = 0
	z = 0

class Object:
	pos = Point()
	ang = Point()


obj1 = Object()
obj2 = Object()

obj1.ang.x = 123

print obj2.ang.x    <<-- AND I FIND IT CONTAINS OBJ1's X VALUE
-------------------------------------------------------------------------



In C, this would be:

-------------------------------------------------------------------------
typedef struct Point {
	float  x;
	float  y;
	float  z;
} Point;

typedef struct Object {
	Point  pos;
	Point  ang;
} Object;

Object obj1;
Object obj2;

obj1.ang.x = 123;
printf("%f", obj2.ang.x);   <<-- AND NOW THE VALUES IN OBJ1 AND OBJ2 
				 WILL NOT BE RELATED (OBJ2 WILL JUST 
				 CONTAIN GARGAGE AT THIS POINT).
-------------------------------------------------------------------------


I've found that writing something like:

class Object(Point):
	...

works, but then I don't have a wrapper around the (x, y, z) values
anymore and I 
don't know how to bring in Point more than once. Is it possible to do
this in Python.  I've looked in the tutorial and Mark Lutz's book to no
avail.

Thanks,
Andy Beall




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