Grease Pencil v3 in Python

Trigger

Use this skill when the user:

• Creates Grease Pencil objects, layers, frames, or strokes from a script
• Mentions grease_pencils, grease_pencils_v3, GreasePencil, GPencilStroke, drawing, add_strokes, or the LINEART modifier
• Ports pre-4.3 GPencil code (frames that carry .strokes directly) to 4.5 LTS or 5.x
• Hits AttributeError on bpy.data.grease_pencils_v3 (5.x), on frame.drawing (legacy data on 4.5), or on the Line Art modifier's thickness (5.x)
• Gets zero Line Art strokes and does not know why

High-level shape

GPv3 exists on both supported versions, but at different addresses. Branch on the bpy.app.version tuple, never on bpy.app.version_string.

import bpy