PyPy2.7 and PyPy3.5 v6.0 dual release

The PyPy team is proud to release both PyPy2.7 v6.0 (an interpreter supporting Python 2.7 syntax), and a PyPy3.5 v6.0 (an interpreter supporting Python 3.5 syntax). The two releases are both based on much the same codebase, thus the dual release.

This release is a feature release following our previous 5.10 incremental release in late December 2017. Our C-API compatibility layer cpyext is now much faster (see the blog post) as well as more complete. We have made many other improvements in speed and CPython compatibility. Since the changes affect the included python development header files, all c-extension modules must be recompiled for this version.

Until we can work with downstream providers to distribute builds with PyPy, we have made packages for some common packages available as wheels. You may compile yourself using pip install --no-build-isolation <package>, the no-build-isolation is currently needed for pip v10.

First-time python users are often stumped by silly typos and omissions when getting started writing code. We have improved our parser to emit more friendly syntax errors, making PyPy not only faster but more friendly.

The GC now has hooks to gain more insights into its performance

The Matplotlib TkAgg backend now works with PyPy, as do pygame and pygobject.

We updated the cffi module included in PyPy to version 1.11.5, and the cppyy backend to 0.6.0. Please use these to wrap your C and C++ code, respectively, for a JIT friendly experience.

As always, this release is 100% compatible with the previous one and fixed several issues and bugs raised by the growing community of PyPy users. We strongly recommend updating.

The Windows PyPy3.5 release is still considered beta-quality. There are open issues with unicode handling especially around system calls and c-extensions.

The utf8 branch that changes internal representation of unicode to utf8 did not make it into the release, so there is still more goodness coming. We also began working on a Python3.6 implementation, help is welcome.

You can download the v6.0 releases here:

We would like to thank our donors for the continued support of the PyPy project. If PyPy is not quite good enough for your needs, we are available for direct consulting work.

We would also like to thank our contributors and encourage new people to join the project. PyPy has many layers and we need help with all of them: PyPy and RPython documentation improvements, tweaking popular modules to run on pypy, or general help with making RPython’s JIT even better.

What is PyPy?

PyPy is a very compliant Python interpreter, almost a drop-in replacement for CPython 2.7 and CPython 3.5. It’s fast (PyPy and CPython 2.7.x performance comparison) due to its integrated tracing JIT compiler.

We also welcome developers of other dynamic languages to see what RPython can do for them.

The PyPy release supports:

  • x86 machines on most common operating systems (Linux 32/64 bits, Mac OS X 64 bits, Windows 32 bits, OpenBSD, FreeBSD)
  • newer ARM hardware (ARMv6 or ARMv7, with VFPv3) running Linux,
  • big- and little-endian variants of PPC64 running Linux,
  • s390x running Linux


  • Speed up C-API method calls, and make most Py*_Check calls C macros
  • Speed up C-API slot method calls
  • Enable TkAgg backend support for matplotlib
  • support hastzinfo and tzinfo in the C-API PyDateTime* structures
  • datetime.h is now more similar to CPython
  • We now support PyUnicode_AsUTF{16,32}String, _PyLong_AsByteArray, _PyLong_AsByteArrayO,
  • PyPy3.5 on Windows is compiled with the Microsoft Visual Compiler v14, like CPython
  • Fix performance of attribute lookup when more than 80 attributes are used
  • Improve performance on passing built-in types to C-API C code
  • Improve the performance of datetime and timedelta by skipping the consistency checks of the datetime values (they are correct by construction)
  • Improve handling of bigint s, including fixing int_divmod
  • Improve reporting of GC statistics
  • Accept unicode filenames in
  • Improve RPython support for half-floats
  • Added missing attributes to C-API instancemethod on pypy3
  • Store error state in thread-local storage for C-API.
  • Fix JIT bugs exposed in the sre module
  • Improve speed of Python parser, improve ParseError messages and SyntaxError
  • Handle JIT hooks more efficiently
  • Fix a rare GC bug exposed by intensive use of cpyext Buffer s

We also refactored many parts of the JIT bridge optimizations, as well as cpyext internals, and together with new contributors fixed issues, added new documentation, and cleaned up the codebase.