Selecting an object via scripting?

Question

As shown below, I have 2 nested spheres, each with a different material (inner = "1", outer = "2"). Ultimately, I need to select the inner sphere (material "1") via python scripting.

I've found a number of ways to select (or make active) one of the spheres. However, even though Blender says that it's selecting the correct sphere (indicated by orange line around center sphere), I don't believe it's active -- adding a modifier applies it to the outer sphere instead. That, and the material properties show the properties of the outer sphere.

Answer 1

bpy.data.objects['Sphere.017']

refers to an object. (Lets assume all names in quotes are the names of objects in your Blender Scene)

2.8 Recent Version of the API

bpy.data.objects["Cube"].select_set(True)
# to select the object in the 3D viewport,

current_state = bpy.data.objects["Cube"].select_get()
# retrieving the current state

# this way you can also select multiple objects

bpy.context.view_layer.objects.active = bpy.data.objects['Sphere']
# to set the active object

https://docs.blender.org/api/current/bpy.types.LayerObjects.html#bpy.types.LayerObjects

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⚠Older Version of API 2.79

A python script can do something with that.

You can also use

bpy.data.objects['Cube'].select = True
# to select the object in the 3D viewport,
# this way you can also select multiple objects

# additionally you can use
bpy.context.scene.objects.active = bpy.data.objects['Sphere.017']
# to make it the active selected object

Answer 2

I'm just doing my duty here. Quick answer that works in 2.8:

objectToSelect = bpy.data.objects["objectName"]
objectToSelect.select_set(True)    
bpy.context.view_layer.objects.active = objectToSelect

You need that last line. Without it I couldn't switch into edit mode. I got the answer here. I wanted to post it here, which is actually the question that comes up when you google this, but it has been locked and now only points to this question which thanks to @piotao pointed me to the answer.

Answer 3

You say that the modifier doesn't get added to the right object - the selected and active objects are only an issue if you are using operators, by directly manipulating data you don't have to bother with what is selected or active unless you want to know the selected object/s as the items that the script will work on.

The line -

mod = bpy.data.objects['Cube'].modifiers.new(name='subsurf',type='SUBSURF')

will add a subsurf modifier to the object named 'Cube' and return the modifier item to the mod variable. You can then use mod.levels = 3 to set the viewport subdivisions and mod.render_levels = 3 to set the render subdivisions.

For the type value of a modifier you can find a list here.