Changes for 1.5#

1.5.0 (2020-04-10)#

1.5a4 (2020-03-23)#

Platform and Packaging Updates#

  • Python version updates: gevent is now tested with CPython 3.6.10, 3.7.7 and 3.8.2. It is also tested with PyPy2 7.3 and PyPy 3.6 7.3.

  • The include directories used to compile the C extensions have been tweaked with the intent of making it easier to use older debug versions of Python. See issue #1461.

  • The binary wheels and installed package no longer include generated C source files and headers. Also excluded are Cython .pxd files, which were never documented. Please file an issue if you miss these.

Library and Dependency Updates#

  • Upgrade libev from 4.25 to 4.31 and update its embedded config.guess to the latest. See issue #1504.


    libev, when built with EV_VERIFY >= 2, now performs verification of file descriptors when IO watchers are started and when they are stopped. If you first close a file descriptor and only then stop an associated watcher, libev will abort the process.

    Using the standard gevent socket and file objects handles this automatically, but if you’re using the IO watchers directly, you’ll need to watch out for this.

    The binary wheels gevent distributes do not set EV_VERIFY and don’t have this issue.

  • Make libuv and libev use the Python memory allocators. This assists with debugging. The event libraries allocate small amounts of memory at startup. The allocation functions have to take the GIL, but because of the limited amount of actual allocation that gets done this is not expected to be a bottleneck.

  • Update the bundled tblib library to the unreleased 1.7.0 version. The only change is to add more attributes to Frame and Code objects for pytest compatibility. See pull request #1541.

Potentially Breaking Changes#

  • Remove the magic proxy object gevent.signal. This served as both a deprecated alias of gevent.signal_handler and the module gevent.signal. This made it confusing to humans and static analysis tools alike. The alias was deprecated since gevent 1.1b4. See issue #1596.


  • Make gevent.subprocess.Popen.communicate raise exceptions raised by reading from the process, like the standard library. In particular, under Python 3, if the process output is being decoded as text, this can now raise UnicodeDecodeError. Reported in issue #1510 by Ofer Koren.

  • Make gevent.subprocess.Popen.communicate be more careful about closing files. Previously if a timeout error happened, a second call to communicate might not close the pipe.

  • Add gevent.contextvars, a cooperative version of contextvars. This is available to all Python versions. On Python 3.7 and above, where contextvars is a standard library module, it is monkey-patched by default. See issue #1407.

  • Use selectors.PollSelector as the selectors.DefaultSelector after monkey-patching if select.poll was defined. Previously, gevent replaced it with selectors.SelectSelector, which has a different set of limitations (e.g., on certain platforms such as glibc Linux, it has a hardcoded limitation of only working with file descriptors < 1024). See issue #1466 reported by Sam Wong.

  • Make the dnspython resolver work if dns python had been imported before the gevent resolver was initialized. Reported in issue #1526 by Chris Utz and Josh Zuech.

1.5a3 (2020-01-01)#

  • Python version updates: gevent is now tested with CPython 2.7.17, 3.5.9, 3.6.9, 3.7.5 and 3.8.0 (final). It is also tested with PyPy2 7.2 and PyPy 3.6 7.2

  • Fix using monkey-patched threading.Lock and threading.RLock objects as spin locks by making them call sleep(0) if they failed to acquire the lock in a non-blocking call. This lets other callbacks run to release the lock, simulating preemptive threading. Using spin locks is not recommended, but may have been done in code written for threads, especially on Python 3. See issue #1464.

  • Fix Semaphore (and monkey-patched threading locks) to be fair. This eliminates the rare potential for starvation of greenlets. As part of this change, the low-level method rawlink of Semaphore, Event, and AsyncResult now always remove the link object when calling it, so unlink can sometimes be optimized out. See issue #1487.

  • Make gevent.pywsgi support Connection: keep-alive in HTTP/1.0. Based on pull request #1331 by tanchuhan.

  • Fix a potential crash using gevent.idle() when using libuv. See issue #1489.

  • Fix some potential crashes using libuv async watchers.

  • Make ThreadPool consistently raise InvalidThreadUseError when spawn is called from a thread different than the thread that created the threadpool. This has never been allowed, but was inconsistently enforced. On gevent 1.3 and before, this would always raise “greenlet error: invalid thread switch,” or LoopExit. On gevent 1.4, it could raise LoopExit, depending on the number of tasks, but still, calling it from a different thread was likely to corrupt libev or libuv internals.

  • Remove some undocumented, deprecated functions from the threadpool module.

  • libuv: Fix a perceived slowness spawning many greenlets at the same time without yielding to the event loop while having no active IO watchers or timers. If the time spent launching greenlets exceeded the switch interval and there were no other active watchers, then the default IO poll time of about .3s would elapse between spawning batches. This could theoretically apply for any non-switching callbacks. This can be produced in synthetic benchmarks and other special circumstances, but real applications are unlikely to be affected. See issue #1493.

  • Fix using the threadpool inside a script or module run with python -m gevent.monkey. Previously it would use greenlets instead of native threads. See issue #1484.

  • Fix potential crashes in the FFI backends if a watcher was closed and stopped in the middle of a callback from the event loop and then raised an exception. This could happen if the hub’s handle_error function was poorly customized, for example. See issue #1482

  • Make gevent.killall stop greenlets from running that hadn’t been run yet. This make it consistent with Greenlet.kill(). See issue #1473 reported by kochelmonster.

  • Make gevent.spawn_raw set the loop attribute on returned greenlets. This lets them work with more gevent APIs, notably gevent.killall(). They already had dictionaries, but this may make them slightly larger, depending on platform (on CPython 2.7 through 3.6 there is no apparent difference for one attribute but on CPython 3.7 and 3.8 dictionaries are initially empty and only allocate space once an attribute is added; they’re still smaller than on earlier versions though).

File Object Changes#


There may be breaking changes here for applications that relied on the old behaviour. The old behaviour was under specified and inconsistent and really only worked consistently with ‘wb’ and ‘rb’ modes, so most applications shouldn’t be affected.

  • The file objects (FileObjectPosix, FileObjectThread) now consistently support text and binary modes. If neither ‘b’ nor ‘t’ is given in the mode, they will read and write native strings. If ‘t’ is given, they will always work with unicode strings, and ‘b’ will always work with byte strings. (FileObjectPosix already worked this way.) See issue #1441.

  • The file objects accept encoding, errors and newline arguments. On Python 2, these are only used if ‘t’ is in the mode.

  • The default mode for FileObjectPosix changed from rb to simply r, for consistency with the other file objects and the standard open and functions.

  • Fix FileObjectPosix improperly being used from multiple greenlets. Previously this was hidden by forcing buffering, which raised RuntimeError.

1.5a2 (2019-10-21)#

  • Add support for CPython 3.8.0. (Windows wheels are not yet available.)

  • Update to Cython 0.29.13 and cffi 1.12.3.

  • Add an --module option to gevent.monkey allowing to run a Python module rather than a script. See pull request #1440.

  • Improve the way joining the main thread works on Python 3.

  • Implement SSLSocket.verify_client_post_handshake() when available.

  • Fix tests when TLS1.3 is supported.

  • Disable Nagle’s algorithm in the backdoor server. This can improve interactive response time.

  • Test on Python 3.7.4. There are important SSL test fixes.

1.5a1 (2019-05-02)#

Platform and Packaging Updates#

  • Python version updates: gevent is now tested with CPython 2.7.16, 3.5.6, 3.6.8, and 3.7.2. It is also tested with PyPy2 7.1 and PyPy 3.6 7.1 (PyPy 7.0 and 7.1 were not capable of running SSL tests on Travis CI).

  • Support for Python 3.4 has been removed, as that version is no longer supported uptstream.

  • gevent binary wheels are now manylinux2010 and include libuv support. pip 19 is needed to install them. See issue #1346.

  • gevent is now compiled with Cython 0.29.6 and cffi 1.12.2.

  • gevent sources include a pyproject.toml file, specifying the build requirements and enabling build isolation. pip 18 or above is needed to take advantage of this. See issue #1180.

  • libev-cffi: Let the compiler fill in the definition of nlink_t for st_nlink in struct stat, instead of trying to guess it ourself. Reported in issue #1372 by Andreas Schwab.

  • Remove the Makefile. Its most useful commands, make clean and make distclean, can now be accomplished in a cross-platform way using python clean and python clean -a, respectively. The remainder of the Makefile contained Travis CI commands that have been moved to .travis.yml.

  • Deprecate the EMBED and LIBEV_EMBED, etc, build-time environment variables. Instead, use GEVENTSETUP_EMBED and GEVENTSETUP_EMBED_LIBEV. See issue #1402.

  • The CFFI backends now respect the embed build-time setting. This allows building the libuv backend without embedding libuv (except on Windows).

  • Support test resources. This allows disabling tests that use the network. See Limiting Resource Usage for more.

Library and Dependency Updates#

  • Upgrade libuv from 1.24.0 to 1.27.0.

  • Upgrade libev from 4.23 to 4.25 and update its embedded config.guess to the latest.

  • Upgrade c-ares from 1.14 to 1.15.

  • dnspython >= 1.16.0 is now required for the dnspython resolver.

Bug fixes#

  • Python 3.7 subprocess: Copy a STARTUPINFO passed as a parameter. Contributed by AndCycle in pull request #1352.

  • subprocess: WIFSTOPPED and SIGCHLD are now handled for determining Popen.returncode. See

  • subprocess: No longer close redirected FDs if they are in pass_fds. This is a bugfix from Python 3.7 applied to all versions gevent runs on.

  • Fix certain operations on a Greenlet in an invalid state (with an invalid parent) to raise a TypeError sooner rather than an AttributeError later. This is also slightly faster on CPython with Cython. Inspired by issue #1363 as reported by Carson Ip. This means that some extreme corner cases that might have passed by replacing a Greenlet’s parent with something that’s not a gevent hub now no longer will.

  • Fix: The spawning_stack for Greenlets on CPython should now have correct line numbers in more cases. See pull request #1379.


  • The result of gevent.ssl.SSLSocket.makefile() can be used as a context manager on Python 2.

  • Python 2: If the backport of the _thread_ module from futures has already been imported at monkey-patch time, also patch this module to be consistent. The pkg_resources package imports this, and pkg_resources is often imported early on Python 2 for namespace packages, so if futures is installed this will likely be the case.

  • Python 2: Avoid a memory leak when an io.BufferedWriter is wrapped around a socket. Reported by Damien Tournoud in issue #1318.

  • Avoid unbounded memory usage when creating very deep spawn trees. Reported in issue #1371 by dmrlawson.

  • Win: Make examples/ do something useful. See pull request #1378 by Robert Iannucci.

  • Spawning greenlets can be up to 10% faster. See pull request #1379.