creating array of python objects

[Faheem Mitha]

Dear People,

I have the current modest goal. Given a user defined class, I want to
creata an array of instances of that class.

Consider the following class.

class cell:
def setrow(self,row):
self.row = row
def setcol(self,col):
self.col = col
...

I create an "empty" cell.

empcell = cell()

Now I want to create an array of objects identical to empcell, and
later initialize them.

I tried stuff along the lines of

************************************************** ****************
import string
from numarray import *

empcell = cell()

base = [empcell]

mat = fromlist(base,shape=(2,2))
************************************************** ****************

But the

mat = fromlist(base,shape=(2,2))

line fails with

AttributeError: cell instance has no attribute '__len__'

Similar things fail with the same error message. No doubt I'm doing
something stupid, but would someone please enlighten me?

I got the fromlist command from

help("numarray.objects")
I was a bit disconcerted to find on trying to run the first example
from the help page that I got
a = fromlist(["t","u","w"])

....
TypeError: Expecting a python numeric type, got something else.

What am I doing wrong?

I'm running

ii python 2.3.3-5 An interactive
high-level object-oriented language (default versio
ii python-numarray 0.8.1-1 An array
processing package modelled after Python-Numeric
ii python-numeric 23.1-1 Numerical
(matrix-oriented) Mathematics for Python

on Debian sarge.

Thanks in advance and sorry for the long-winded message.

Faheem.

[Jeff Epler]

I don't believe that numarray supports arrays of Python objects.
The list of Numarray types doesn't list them:
http://stsdas.stsci.edu/numarray/num...ype-specifiers

This is the meaning of the "not a numeric type" message.

Using numpy, you can create an array of PyObjects where each entry is a
reference to the same cell object:

class cell: ... def setrow(self,row):
... self.row = row
... def setcol(self,col):
... self.col = col
... empcell = cell()
a = Numeric.reshape([empcell]*4, (2,2))
a[0][0].setrow(10)
a[1][1].row # because they are the same object 10
If you want distinct objects, you'll have to use a = Numeric.reshape([cell() for i in range(4)], (2,2))

Jeff

[Faheem Mitha]

On Sun, 14 Mar 2004, Jeff Epler wrote:

I don't believe that numarray supports arrays of Python objects.
The list of Numarray types doesn't list them:
http://stsdas.stsci.edu/numarray/num...ype-specifiers

This is the meaning of the "not a numeric type" message.
Todd Miller said some stuff had not been documented yet. In any case, this
is from a numarray help page!
Using numpy, you can create an array of PyObjects where each entry is a
reference to the same cell object:

>>> class cell: ... def setrow(self,row):
... self.row = row
... def setcol(self,col):
... self.col = col
... >>> empcell = cell()
>>> a = Numeric.reshape([empcell]*4, (2,2))
>>> a[0][0].setrow(10)
>>> a[1][1].row # because they are the same object 10
If you want distinct objects, you'll have to use >>> a = Numeric.reshape([cell() for i in range(4)], (2,2))

Jeff

Thanks for the info. However, I was going by

numarray.objects

FILE
/usr/lib/python2.3/site-packages/numarray/objects.py

DESCRIPTION
objects -- This module defines a class and set of functions for
manipulating arrays of Python objects. It defines functions which
correspond to most of the most of the operators defined in Python's
operator module, and provides names compatible with most of numarray's
universal functions.
...

I thought this meant I *could* create an array of python objects. Am I
misunderstanding something?

Thanks for the help.
Faheem.

[Terry Reedy]

"Faheem Mitha" <fa****@email.unc.edu> wrote in message
news:sl*******************@Chrestomanci.home.earth ...

Dear People,

I have the current modest goal. Given a user defined class, I want to
creata an array of instances of that class.

Given that the purpose of Numerical Python and NumArray are to make
available fast unboxed raw number array computations, I wonder whether a
plain old simple list of lists wouldn't serve your purpose, at least for
prototyping:

Cells = [[cell(),cell()], [cell(),cell()]]
# easily generalized with nested list comprehensions.

Terry J. Reedy

[Faheem Mitha]

On Sun, 14 Mar 2004 13:37:36 -0600, Jeff Epler <je****@unpythonic.net> wrote:

I don't believe that numarray supports arrays of Python objects.
The list of Numarray types doesn't list them:
http://stsdas.stsci.edu/numarray/num...ype-specifiers

This is the meaning of the "not a numeric type" message.

Using numpy, you can create an array of PyObjects where each entry is a
reference to the same cell object:

>>> class cell: ... def setrow(self,row):
... self.row = row
... def setcol(self,col):
... self.col = col
... >>> empcell = cell()
>>> a = Numeric.reshape([empcell]*4, (2,2))
>>> a[0][0].setrow(10)
>>> a[1][1].row # because they are the same object 10
Is a[0,0] equivalent to a[0][0]? It is a slightly more compact representation.
If you want distinct objects, you'll have to use >>> a = Numeric.reshape([cell() for i in range(4)], (2,2))

Thanks. Faheem.