What’s new in gevent 1.2#

Detailed information on what has changed is available in Changes for 1.2. This document summarizes the most important changes since gevent 1.1.

In general, gevent 1.2 is a smaller update than gevent 1.1, focusing on platform support, standard library compatibility, security, bug fixes and consistency.

Platform Support#

gevent 1.2 supports Python 2.7, 3.4, 3.5 and 3.6 on the CPython (python.org) interpreter. It also supports PyPy2 4.0.1 and above (PyPy2 5.4 or higher is recommended) and PyPy3 5.5.0.


Support for Python 2.6 was removed. Support for Python 3.3 is only tested on PyPy3.


PyPy is not supported on Windows. (gevent’s CFFI backend is not available on Windows.)

Python 3.6 was released recently and is supported at the same level as 3.5.

For ease of installation on Windows and OS X, gevent 1.2 is distributed as pre-compiled binary wheels, in addition to source code.

Bug Fixes#

Since 1.1.2, gevent 1.2 contains over 240 commits from nine different dozen contributors. About two dozen pull requests were merged.

Improved subprocess support#

In gevent 1.1, subprocess monkey-patching was on by default for the first time. Over time this led to discovery of a few issues and corner cases that have been fixed in 1.2.

  • Setting SIGCHLD to SIG_IGN or SIG_DFL after gevent.subprocess had been used previously could not be reversed, causing Popen.wait and other calls to hang. Now, if SIGCHLD has been ignored, the next time gevent.subprocess is used this will be detected and corrected automatically. (This potentially leads to issues with os.popen() on Python 2, but the signal can always be reset again. Mixing the low-level process handling calls, low-level signal management and high-level use of gevent.subprocess is tricky.) Reported in issue #857 by Chris Utz.

  • Popen.kill and send_signal no longer attempt to send signals to processes that are known to be exited.

  • The gevent.os.waitpid() function is cooperative in more circumstances. Reported in issue #878 by Heungsub Lee.

API Additions#

Numerous APIs offer slightly expanded functionality in this version. Look for “changed in version 1.2” or “added in version 1.2” throughout the documentation for specifics.

Of particular note, several backwards compatible updates to the subprocess module have been backported from Python 3 to Python 2, making gevent.subprocess smaller, easier to maintain and in some cases safer, while letting gevent clients use the updated APIs even on older versions of Python.

If concurrent.futures is available (Python 3, or if the Python 2 backport has been installed), then the class gevent.threadpool.ThreadPoolExecutor is defined to create an executor that always uses native threads, even when the system is monkey-patched.

Library Updates#

The two C libraries that are bundled with gevent have been updated. libev has been updated from 4.20 to 4.23 (libev release notes) and c-ares has been updated from 1.10.0 to 1.12.0 (c-ares release notes).


This release is intended to be compatible with 1.1.x with no changes to client source code, so long as only non-deprecated and supported interfaces were used (as always, internal, non-documented implementation details may have changed).

In particular the deprecated gevent.coros module has been removed and gevent.corecext and gevent.corecffi have also been removed.

For security, gevent.pywsgi no longer accepts incoming headers containing an underscore, and header values passed to start_response cannot contain a carriage return or newline. See issue #819 and issue #775, respectively.