Start coding for Blender
Blender core is coded in C. Some part like Cycles are coded in C++. Python is widely used for extending Blender functionalities with scripts and addons.
(For BlenderBIM Addon specific code see BlenderBIM Add-on code examples)
C/C++
Blender foundation made a video to present code structure :
python
Introduction
Good introduction to python use in Blender from Curtis Holt :
To learn more checkout the Blender Python API documentation especially Quickstart part.
Tips and Tricks
From Blender Python API doc
Blender Python API documentation has a special Tips and Tricks chapter including external editor usage, inserting a python interpreter etc…
bpy stubs for auto-completion
Main known project which provide stubs for auto-completion is [fake-bpy-module](https://github.com/nutti/fake-bpy-module). It also provide type hints for python >= 3.7 which should allow to perform type checking (eg. mypy).
