![This PEP proposes the merger of the Unladen Swallow project [3] into CPython's source tree. Unladen Swallow is an open-source branch of CPython focuse](https://www.python.org/static/opengraph-icon-200x200.png "PEP 3146 -- Merging Unladen Swallow into CPython | Python.org"){kind=icon}
PEP 3146 -- Merging Unladen Swallow into CPython | Python.org
This PEP proposes the merger of the Unladen Swallow project [3] into CPython's source tree. Unladen Swallow is an open-source branch of CPython focused on performance. Unladen Swallow is source-compatible with valid Python 2.6.4 applications and C extension modules.
Unladen Swallow adds a just-in-time (JIT) compiler to CPython, allowing for the compilation of selected Python code to optimized machine code. Beyond classical static compiler optimizations, Unladen Swallow's JIT compiler takes advantage of data collected at runtime to make checked assumptions about code behaviour, allowing the production of faster machine code.
This PEP proposes to integrate Unladen Swallow into CPython's development tree in a separate py3k-jit branch, targeted for eventual merger with the main py3k branch. While Unladen Swallow is by no means finished or perfect, we feel that Unladen Swallow has reached sufficient maturity to warrant incorporation into CPython's roadmap. We have sought to create a stable platform that the wider CPython development team can build upon, a platform that will yield increasing performance for years to come.
This PEP will detail Unladen Swallow's implementation and how it differs from CPython 2.6.4; the benchmarks used to measure performance; the tools used to ensure correctness and compatibility; the impact on CPython's current platform support; and the impact on the CPython core development process. The PEP concludes with a proposed merger plan and brief notes on possible directions for future work.
