pyssa: An Executable, Source-Oriented, Stable Intermediate Representation for Python

Python analysis and transformation workflows are often forced to use one of two awkward input formats:

• Python AST, which preserves source well and is stable, but does not present executable control flow
• Python bytecode, which is executable but does not preserve source and inherits unstable implementation details that are not always desirable for analysis and transformation

pyssa takes a different path. It lowers Python source into a region-based, explicit control-flow IR that is still close to source but can be executed directly and serves as a stable substrate for future analysis and transformation workflows.

The current prototype already supports lowering from Python source, execution through an interpreter, and validation against CPython for a substantial subset of Python. The prototype is accessible at https://github.com/jifengwu2k/pyssa.