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pypy / pypy / doc / release-2.0.0.rst

PyPy 2.0 - Einstein Sandwich

We're pleased to announce PyPy 2.0. This is a stable release that brings a swath of bugfixes, small performance improvements and compatibility fixes.

You can download the PyPy 2.0 release here:


The two biggest changes since PyPy 1.9 are:

  • stackless is now supported including greenlets, which means eventlet and gevent should work (but read below about gevent)
  • PyPy now contains release 0.6 of cffi as a builtin module, which is preferred way of calling C from Python that works well on PyPy

What is PyPy?

PyPy is a very compliant Python interpreter, almost a drop-in replacement for CPython 2.7. It's fast (pypy 2.0 and cpython 2.7.3 performance comparison) due to its integrated tracing JIT compiler.

This release supports x86 machines running Linux 32/64, Mac OS X 64 or Windows 32. Windows 64 work is still stalling, we would welcome a volunteer to handle that. ARM support is on the way and we're expecting to release an alpha ARM version shortly.


  • Stackless including greenlets should work. For gevent, you need to check out pypycore and use the pypy-hacks branch of gevent.
  • cffi is now a module included with PyPy. (cffi also exists for CPython; the two versions should be fully compatible.) It is the preferred way of calling C from Python that works on PyPy.
  • Callbacks from C are now JITted, which means XML parsing is much faster.
  • A lot of speed improvements in various language corners, most of them small, but speeding up some particular corners a lot.
  • The JIT was refactored to emit machine code which manipulates a "frame" that lives on the heap rather than on the stack. This is what makes Stackless work, and it could bring another future speed-up (not done yet).
  • A lot of stability issues fixed.

Cheers, fijal, arigo and the PyPy team