Question

I have a library of component objects. I would like to include instantiations of a selection of those objects in another object. But I would like to provide that selection as a list so that each time I instantiate the container object with a list, it will be created with the specified sub objects in it.

Let’s say my component library looks like this:

class ColorBlob(object):
    ...
    def wipeItUp()
        ...

class RedBlob(ColorBlob):
    ...
    def paintIt()
        ...
class YellowBlob(ColorBlob):
    ...
    def paintIt()
        ...
class BlueBlob(ColorBlob):
    ...
    def paintIt()
        ...

And my container object looks like this:

class Pallet(object):
    def __init__(self, colorList):
        for color in colorList:
            #Ok, here is where I get lost if I know the color I can do this:
            Pallet.BlueBlob = blobLib.BlueBlob()
            #But I don't, so I am trying to do something like this:
            blobSpecs       = getattr(blobLib, color)
            blobSpecs.Obj   = blobSpecs().returnObj(self.page) # with "returnObj" defined in the library as some other method
            setattr(self, Pallet.blobName, blobSpecs) #and I am completely lost.

But what I really want to do in my functional code is this:

workingPallet=Pallet(['RedBlob', 'BlueBlob'])
workingPallet.RedBlob.paintIt()

I know that I am lost when I try to instantiate the sub objects in the container. Can someone help me straighten out my “getattr” and “setattr” nonsense?

Answer 1

You were almost there, but it isn’t your getattr or setattr that’s the problem. You end up setting the class back on self, not the instance you created:

def __init__(self, colorList):
    for color in colorList:
        blobSpec       = getattr(blobLib, color)
        blob           = blobSpec()    # create an instance of the blob
        blob.Obj       = blob.returnObj(self.page) 
        setattr(self, color, blob)

It’s the same thing as calling the class directly (BlueBlob()), but now through a variable.