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Importing and Reloading Python Modules in Blender

Python in Blender can be tiring. A simple problem becomes an arduous trek through docs, examples, and sometimes the C API to find the Blender way to write given Python code. This is due to the many quirks of Blender's own internal Python environment.

Importing is one of those arduous tasks. Python provides a lot of functionality to import all different kinds of source and data files but Blender's implementation makes design decisions that create issues. This is my deep dive into Blender's Python import integration where at the end I provide a small module to make your future Blender importing life easier.


In a nutshell, Python's module importing/loading comes bundled in the from ... import ... as ... syntax. This syntax ultimately compiles to various forms of the __import__() function. Instead of interfacing with this directly, Python provides importlib in Python 3.4+ (previously imp in Python < 3.4) to make interfacing with __import__() much easier. Blender decides to forgo this setup for its own implementation with the intention of making their own integration work better with the way Blender handles its data. This allows it to support nifty features like code files being text datablocks and inline python snippets in other parts of the application.

Unfortunately this override seems to break some functionality including relative imports and simply makes other tasks like how to structure a multi-file project confusing. This is a real bummer for large Blender applications. The above StackOverflow answer recommends appending to sys.path which works just fine but leaves a more comprehensive system to be desired. Things like module reloading for easy development and the ability to register and unregister large applications at will to support the little checkbox in the User Preferences window.

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