Dynamically created objects

[=?ISO-8859-1?Q?Michael_Bernhard_Arp_S=F8rensen?=]

Hi there.

I need to create objects on the fly in my program. The names of the
objects must be unique, obviously, and I need to put them in a list for
later use.

How do i set the name of an object if the name is stored in another
variable?

I've looked in the O'Reiley Python Cookbook and on google, but no joy.

Thanks in advance.

/Tram

[Gabriel Genellina]

En Fri, 28 Dec 2007 04:14:43 -0300, Michael Bernhard Arp Sørensen
<mu*************@gmail.comescribió:

I need to create objects on the fly in my program. The names of the
objects must be unique, obviously, and I need to put them in a list for
later use.

How do i set the name of an object if the name is stored in another
variable?

I've looked in the O'Reiley Python Cookbook and on google, but no joy.

Use a dictionary as a container.

pyns = {}
pyname = "Joe"
pyo = object()
pyns[name] = o
pyanother = set("another")
pyns["another"] = another
pyns
{'Joe': <object object at 0x009D0478>,
'another': set(['a', 'e', 'h', 'o', 'n', 'r', 't'])}

--
Gabriel Genellina

[Steven D'Aprano]

On Fri, 28 Dec 2007 08:14:43 +0100, Michael Bernhard Arp Sørensen wrote:

Hi there.

I need to create objects on the fly in my program. The names of the
objects must be unique, obviously, and I need to put them in a list for
later use.

Why do you think they need names? If you have them in a list, just refer
to them by the list and index. Or a dict and a key.

E.g. instead of this:
# this doesn't work
for i in range(10):
"foo" + i = "some data here" # variables like foo0, foo1 ...
process(foo0, foo1, foo2)

do this:

foo = []
for i in range(10):
foo.append("some data here")
process(foo[0], foo[1], foo[2])

How do i set the name of an object if the name is stored in another
variable?

If you really need to do this, and I doubt that you do, here's one way:

>>bird

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'bird' is not defined

>>globals()["bird"] = "a parrot with beautiful plumage"
bird

'a parrot with beautiful plumage'
If you're tempted to try the same trick with locals(), don't bother -- it
won't reliably work.

If you are absolutely sure that the data is safe (i.e. you control it,
not random users via a web form) you can also use exec.

--
Steven