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.