I have an object with a container in it. Is there a way, in a script, to set the size of the object?

No. However you could use hidden tabs with different sizes on them. What's the purpose of this?

Trying to display one or more images in a certain space.

Thanks for your help.

Yes I think making a tab panel for each image size would work well for that. In fact I did something like that for a client, using SuperContainer. One of its advantages is that it creates multiple thumbnail sizes as needed, which can potentially speed things up quite a bit.