PyPy v7.3.5: release of 2.7 and 3.7


This is a pre-release announcement. When the release actually happens, it will be announced on the PyPy blog

We are releasing a PyPy 7.3.5 with bugfixes for PyPy 7.3.4, released April 4. PyPy 7.3.4 was the first release that runs on windows 64-bit, so that support is still “beta”. We are releasing it in the hopes that we can garner momentum for its continued support, but are already aware of some problems, for instance it errors in the NumPy test suite (issue 3462). Please help out with testing the releae and reporting successes and failures, financially supporting our ongoing work, and helping us find the source of these problems.

  • The new windows 64-bit builds improperly named c-extension modules with the same extension as the 32-bit build (issue 3443)

  • Use the windows-specific PC/pyconfig.h rather than the posix one

  • Fix the return type for _Py_HashDouble which impacts 64-bit windows

  • A change to the python 3.7 sysconfig.get_config_var('LIBDIR') was wrong, leading to problems finding for embedded PyPy (issue 3442).

  • Instantiate distutils.command.install schema for PyPy-specific implementation_lower

  • Delay thread-checking logic in greenlets until the thread is actually started (continuation of issue 3441)

  • Four upstream (CPython) security patches were applied: - BPO 42988 to remove pydoc.getfile - BPO 43285 to not trust the PASV response in ftplib. - BPO 43075 to remove a possible ReDoS in urllib AbstractBasicAuthHandler - BPO 43882 to sanitize urls containing ASCII newline and tabs in


  • Fix for json-specialized dicts (issue 3460)

  • Specialize ByteBuffer.setslice which speeds up binary file reading by a factor of 3

  • When assigning the full slice of a list, evaluate the rhs before clearing the list (issue 3440)

  • On Python2, PyUnicode_Contains accepts bytes as well as unicode.

  • Update the packaged sqlite3 to 3.35.5 on windows. While not a bugfix, this seems like an easy win.

We recommend updating. These fixes are the direct result of end-user bug reports, so please continue reporting issues as they crop up.

You can find links to download the v7.3.5 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. If PyPy is helping you out, we would love to hear about it and encourage submissions to our renovated blog site via a pull request to

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.

If you are a python library maintainer and use C-extensions, please consider making a CFFI / cppyy version of your library that would be performant on PyPy. In any case both cibuildwheel and the multibuild system support building wheels for PyPy.

What is PyPy?

PyPy is a Python interpreter, a drop-in replacement for CPython 2.7, 3.7, and soon 3.8. It’s fast (PyPy and CPython 3.7.4 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.

This PyPy release supports:

  • x86 machines on most common operating systems (Linux 32/64 bits, Mac OS X 64 bits, Windows 32/64 bits, OpenBSD, FreeBSD)
  • big- and little-endian variants of PPC64 running Linux,
  • s390x running Linux
  • 64-bit ARM machines running Linux.

PyPy does support ARM 32 bit processors, but does not release binaries.