python references

[dustin.getz]

>>from Numeric import zeros

>>p=zeros(3)
p

array([0,0,0])

>>p[0]

0

>>x=p[0]
x=10
p

array([0,0,0]) #actual behavior
#array([10,0,0]) #desired behavior

I want x to be a C++-esque reference to p[0] for convenience in a
vector3 class. i dont want accessor methods. i know python can do
this, but it's been a long time since I used it and am unsuccessful in
my googling and docreading. a little help please?

[Diez B. Roggisch]

du*********@gmail.com wrote:

>>>from Numeric import zeros
p=zeros(3)
p

array([0,0,0])

>>>p[0]

0

>>>x=p[0]
x=10
p

array([0,0,0]) #actual behavior
#array([10,0,0]) #desired behavior

I want x to be a C++-esque reference to p[0] for convenience in a
vector3 class. i dont want accessor methods. i know python can do
this, but it's been a long time since I used it and am unsuccessful in
my googling and docreading. a little help please?

Nope, python can't do this.

Diez

[Rob Wolfe]

du*********@gmail.com wrote:

>from Numeric import zeros
p=zeros(3)
p

array([0,0,0])

>p[0]

0

>x=p[0]

`x' is now a reference to immutable integer object
with value 0, not to first element of array `p'

>x=10

now `x' is a reference to immutable integer object
with value 10, array doesn't change

>p

array([0,0,0]) #actual behavior
#array([10,0,0]) #desired behavior

I want x to be a C++-esque reference to p[0] for convenience in a
vector3 class. i dont want accessor methods. i know python can do
this, but it's been a long time since I used it and am unsuccessful in
my googling and docreading. a little help please?

You can have such a reference to mutable objects.
Consider this:

>>p = [[0,0,0], [0,0,0]]
x = p[0] # reference to mutable list object
x[0] = 10
p

[[10, 0, 0], [0, 0, 0]]

--
HTH,
Rob