How to display EnumProperty control like radio buttons, while keeping the selection exclusive? I have an EnumProperty set up on the Scene in the register function:

def register():
    bpy.types.Scene.my_enum = bpy.props.EnumProperty(
        name = "My enum",
        description = "My enum description",
        items = [
            ("FIRST" , "First one" , "Description..."),
            ("SECNOD", "Second one", "Some other description")
        ]
    )


Now, elsewhere in the code I have a Panel, which is to display the 'enum' for selection:

class SomePanel(bpy.types.Panel):
    bl_idname      = "some_panel"
    bl_label       = "A panel"
    bl_space_type  = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context     = "render"

    def draw(self, context):
        layout = self.layout
        scene = context.scene
        layout.prop(scene, "my_enum")


So far so good, the control draws correctly, but not the way I want:





Thing is - I wanted a different appearance - I didn't want a dropdown field, instead I want a radio-button like field, as the one found for example here:



... where I can choose one of the options regarding the color mode (BW , RGB or RGBA). 

I've found that I can put the "ENUM_FLAG" in the options field of the EnumProperty definition:

def register():
        bpy.types.Scene.my_enum = bpy.props.EnumProperty(
            name = "My enum",
            description = "My enum description",
            items = [
                ("FIRST" , "First one" , "Description..."),
                ("SECNOD", "Second one", "Some other description")
            ],
            options = {"ENUM_FLAG"}
        )


This too worked fine, the result I got now is this:



But now I can activate both buttons at once using Shift, and that's what I want to avoid:



So How can make the selection exclusive? How to force Blender to switch from one option to the other (or in other words: How to disable the Shift functionality)?
Booleans have toggle=True, and Enums have expand=True

layout.prop(scene, "my_enum", expand=True)




The most extensive UI cookbook is still this one though the layout docs are definitely useful after you've struggled a little. Other than those two sources I find it best to read through the draw functions of the add-ons supplied with Blender (you probably did this already.. if not, do)