24.2.1 (2024-02-14)#


  • Add support for Python patch releases 3.11.8 and 3.12.2, which changed internal details of threading.

    As a result of these changes, note that it is no longer possible to change the __class__ of a gevent.threading._DummyThread object on those versions.

    See issue #2020.


Other updates for compatibility with the standard library include:

  • Errors raised from subprocess.Popen may not have a filename set.

  • SSLSocket.recv_into and no longer require the buffer to implement len and now work with buffers whose size is not 1.

  • gh-108310: Fix CVE-2023-40217: Check for & avoid the ssl pre-close flaw.

In addition:

  • Drop setuptools to a soft test dependency.

  • Drop support for very old versions of CFFI.

  • Update bundled c-ares from 1.19.1 to 1.26.0.

  • Locks created by gevent, but acquired from multiple different threads (not recommended), no longer spin to implement timeouts and interruptible blocking. Instead, they use the native functionality of the Python 3 lock. This may improve some scenarios. See issue #2013.

23.9.1 (2023-09-12)#


  • Require greenlet 3.0 on Python 3.11 and Python 3.12; greenlet 3.0 is recommended for all platforms. This fixes a number of obscure crashes on all versions of Python, as well as fixing a fairly common problem on Python 3.11+ that could manifest as either a crash or as a SystemError. See issue #1985.

23.9.0.post1 (2023-09-02)#

  • Fix Windows wheel builds.

  • Fix macOS wheel builds.

23.9.0 (2023-09-01)#


  • Make accept arbitrary iterables, not just sequences. That is, you can now pass in a generator of file descriptors instead of a realized list. Internally, arbitrary iterables are copied into lists. This better matches what the standard library does. Thanks to David Salvisberg. See issue #1979.

  • On Python 3.11 and newer, opt out of Cython’s fast exception manipulation, which may be causing problems in certain circumstances when combined with greenlets.

    On all versions of Python, adjust some error handling in the default C-based loop. This fixes several assertion failures on debug versions of CPython. Hopefully it has a positive impact under real conditions. See issue #1985.

  • Make gevent.pywsgi comply more closely with the HTTP specification for chunked transfer encoding. In particular, we are much stricter about trailers, and trailers that are invalid (too long or featuring disallowed characters) forcibly close the connection to the client after the results have been sent.

    Trailers otherwise continue to be ignored and are not available to the WSGI application.

    Previously, carefully crafted invalid trailers in chunked requests on keep-alive connections might appear as two requests to gevent.pywsgi. Because this was handled exactly as a normal keep-alive connection with two requests, the WSGI application should handle it normally. However, if you were counting on some upstream server to filter incoming requests based on paths or header fields, and the upstream server simply passed trailers through without validating them, then this embedded second request would bypass those checks. (If the upstream server validated that the trailers meet the HTTP specification, this could not occur, because characters that are required in an HTTP request, like a space, are not allowed in trailers.) CVE-2023-41419 was reserved for this.

    Our thanks to the original reporters, Keran Mu ( and Jianjun Chen (, from Tsinghua University and Zhongguancun Laboratory. See issue #1989.

23.7.0 (2023-07-11)#


  • Add preliminary support for Python 3.12, using greenlet 3.0a1. This is somewhat tricky to build from source at this time, and there is one known issue: On Python 3.12b3, dumping tracebacks of greenlets is not available. issue #1969.

  • Update the bundled c-ares version to 1.19.1. See issue #1947.


  • Fix an edge case connecting a non-blocking SSLSocket that could result in an AttributeError. In a change to match the standard library, calling sock.connect_ex() on a subclass of socket no longer calls the subclass’s connect method.

    Initial fix by Priyankar Jain. See issue #1932.

  • Make gevent’s FileObjectThread (mostly used on Windows) implement readinto cooperatively. PR by Kirill Smelkov. See issue #1948.

  • Work around an AttributeError during cyclic garbage collection when Python finalizers (__del__ and the like) attempt to use gevent APIs. This is not a recommended practice, and it is unclear if catching this AttributeError will fix any problems or just shift them. (If we could determine the root situation that results in this cycle, we might be able to solve it.) See issue #1961.

Deprecations and Removals#

  • Remove support for obsolete Python versions. This is everything prior to 3.8.

    Related changes include:

    • Stop using pkg_resources to find entry points (plugins). Instead, use importlib.metadata.

    • Honor sys.unraisablehook when a callback function produces an exception, and handling the exception in the hub also produces an exception. In older versions, these would be simply printed.

    • no longer includes the setup_requires keyword. Installation with a tool that understands pyproject.toml is recommended.

    • The bundled tblib has been updated to version 2.0.

22.10.2 (2022-10-31)#


  • Update to greenlet 2.0. This fixes a deallocation issue that required a change in greenlet’s ABI. The design of greenlet 2.0 is intended to prevent future fixes and enhancements from requiring an ABI change, making it easier to update gevent and greenlet independently.


    greenlet 2.0 requires a modern-ish C++ compiler. This may mean certain older platforms are no longer supported. See issue #1909.

22.10.1 (2022-10-14)#



22.08.0 (2022-10-08)#


  • Windows: Test and provide binary wheels for PyPy3.7.

    Note that there may be issues with subprocesses, signals, and it may be slow. See issue #1798.

  • Upgrade embedded c-ares to 1.18.1. See issue #1847.

  • Upgrade bundled libuv to 1.42.0 from 1.40.0. See issue #1851.

  • Added preliminary support for Python 3.11 (rc2 and later).

    Some platforms may or may not have binary wheels at this time.


    Support for legacy versions of Python, including 2.7 and 3.6, will be ending soon. The maintenance burden has become too great and the maintainer’s time is too limited.

    Ideally, there will be a release of gevent compatible with a final release of greenlet 2.0 that still supports those legacy versions, but that may not be possible; this may be the final release to support them.

    gevent.threadpool.ThreadPool can now optionally expire idle threads. This is used by default in the implicit thread pool used for DNS requests and other user-submitted tasks; other uses of a thread-pool need to opt-in to this. See issue #1867.


  • Truly disable the effects of compiling with -ffast-math. See issue #1864.

21.12.0 (2021-12-11)#


  • Update autoconf files for Apple Silicon Macs. Note that while there are reports of compiling gevent on Apple Silicon Macs now, this is not a tested configuration. There may be some remaining issues with CFFI on some systems as well. See issue #1721.

  • Build and upload CPython 3.10 binary manylinux wheels.

    Unfortunately, this required us to stop building and uploading CPython 2.7 binary manylinux wheels. Binary wheels for 2.7 continue to be available for Windows and macOS. See issue #1822.

  • Test and distribute musllinux_1_1 wheels. See issue #1837.

  • Update the tested versions of PyPy2 and PyPy3. For PyPy2, there should be no user visible changes, but for PyPy3, support has moved from Python 3.6 to Python 3.7. See issue #1843.


  • Try to avoid linking to two different Python runtime DLLs on Windows. See issue #1814.

  • Stop compiling manylinux wheels with -ffast-math. This was implicit in -Ofast, but could alter the global state of the process. Analysis and fix thanks to Ilya Konstantinov. See issue #1820.

  • Fix hanging the interpreter on shutdown if gevent monkey patching occurred on a non-main thread in Python 3.9.8 and above. (Note that this is not a recommended practice.) See issue #1839.

21.8.0 (2021-08-05)#


  • Update the embedded c-ares from 1.16.1 to 1.17.1. See issue #1758.

  • Add support for Python 3.10rc1 and newer.

    As part of this, the minimum required greenlet version was increased to 1.1.0 (on CPython), and the minimum version of Cython needed to build gevent from a source checkout is 3.0a9.

    Note that the dnspython resolver is not available on Python 3.10. See issue #1790.

  • Update from Cython 3.0a6 to 3.0a9. See issue #1801.


21.1.2 (2021-01-20)#


  • Update the embedded libev from 4.31 to 4.33. See issue #1754.

  • Update the embedded libuv from 1.38.0 to 1.40.0. See issue #1755.


21.1.1 (2021-01-18)#


Fix a TypeError on startup on Python 2 with zope.schema installed. Reported by Josh Zuech.

21.1.0 (2021-01-15)#


  • Make gevent FileObjects more closely match the semantics of native file objects for the name attribute:

    • Objects opened from a file descriptor integer have that integer as their name. (Note that this is the Python 3 semantics; Python 2 native file objects returned from os.fdopen() have the string “<fdopen>” as their name , but here gevent always follows Python 3.)

    • The name remains accessible after the file object is closed.

    Thanks to Dan Milon. See issue #1745.


Make gevent.event.AsyncResult print a warning when it detects improper cross-thread usage instead of hanging.

AsyncResult has never been safe to use from multiple threads. It, like most gevent objects, is intended to work with greenlets from a single thread. Using AsyncResult from multiple threads has undefined semantics. The safest way to communicate between threads is using an event loop async watcher.

Those undefined semantics changed in recent gevent versions, making it more likely that an abused AsyncResult would misbehave in ways that could cause the program to hang.

Now, when AsyncResult detects a situation that would hang, it prints a warning to stderr. Note that this is best-effort, and hangs are still possible, especially under PyPy 7.3.3.

At the same time, AsyncResult is tuned to behave more like it did in older versions, meaning that the hang is once again much less likely. If you were getting lucky and using AsyncResult successfully across threads, this may restore your luck. In addition, cross-thread wakeups are faster. Note that the gevent hub now uses an extra file descriptor to implement this.

Similar changes apply to gevent.event.Event (see issue #1735).

See issue #1739.

20.12.1 (2020-12-27)#


  • Make gevent.Greenlet objects function as context managers. When the with suite finishes, execution doesn’t continue until the greenlet is finished. This can be a simpler alternative to a gevent.pool.Group when the lifetime of greenlets can be lexically scoped.

    Suggested by André Caron. See issue #1324.


  • Make gevent’s Semaphore objects properly handle native thread identifiers larger than can be stored in a C long on Python 3, instead of raising an OverflowError.

    Reported by TheYOSH. See issue #1733.

20.12.0 (2020-12-22)#



  • Incorrectly passing an exception instance instead of an exception type to gevent.Greenlet.kill or gevent.killall no longer prints an exception to stderr. See issue #1663.

  • Make destroying a hub try harder to more forcibly stop loop processing when there are outstanding callbacks or IO operations scheduled.

    Thanks to Josh Snyder (issue #1686) and Jan-Philip Gehrcke (issue #1669). See issue #1686.

  • Improve the ability to use monkey-patched locks, and gevent.lock.BoundedSemaphore, across threads, especially when the various threads might not have a gevent hub or any other active greenlets. In particular, this handles some cases that previously raised LoopExit or would hang. Note that this may not be reliable on PyPy on Windows; such an environment is not currently recommended.

    The semaphore tries to avoid creating a hub if it seems unnecessary, automatically creating one in the single-threaded case when it would block, but not in the multi-threaded case. While the differences should be correctly detected, it’s possible there are corner cases where they might not be.

    If your application appears to hang acquiring semaphores, but adding a call to gevent.get_hub() in the thread attempting to acquire the semaphore before doing so fixes it, please file an issue. See issue #1698.

  • Make error reporting when a greenlet suffers a RecursionError more reliable.

    Reported by Dan Milon. See issue #1704.

  • gevent.pywsgi: Avoid printing an extra traceback (“TypeError: not enough arguments for format string”) to standard error on certain invalid client requests.

    Reported by Steven Grimm. See issue #1708.

  • Add support for PyPy2 7.3.3. See issue #1709.

  • Python 2: Make gevent.subprocess.Popen.stdin objects have a write method that guarantees to write the entire argument in binary, unbuffered mode. This may require multiple trips around the event loop, but more closely matches the behaviour of the Python 2 standard library (and gevent prior to 1.5). The number of bytes written is still returned (instead of None). See issue #1711.

  • Make gevent.pywsgi stop trying to enforce the rules for reading chunked input or Content-Length terminated input when the connection is being upgraded, for example to a websocket connection. Likewise, if the protocol was switched by returning a 101 status, stop trying to automatically chunk the responses.

    Reported by Kavindu Santhusa. See issue #1712.

  • Remove the __dict__ attribute from gevent.socket.socket objects. The standard library socket do not have a __dict__.

    Noticed by Carson Ip.

    As part of this refactoring, share more common socket code between Python 2 and Python 3. See issue #1724.

20.9.0 (2020-09-22)#


  • The embedded libev is now asked to detect the availability of clock_gettime and use the realtime and/or monotonic clocks, if they are available.

    On Linux, this can reduce the number of system calls libev makes. Originally provided by Josh Snyder. See issue #1648.


  • On CPython, depend on greenlet >= 0.4.17. This version is binary incompatible with earlier releases on CPython 3.7 and later.

    On Python 3.7 and above, the module gevent.contextvars is no longer monkey-patched into the standard library. contextvars are now both greenlet and asyncio task local. See issue #1656. See issue #1674.

  • The DummyThread objects created automatically by certain operations when the standard library threading module is monkey-patched now match the naming convention the standard library uses (“Dummy-12345”). Previously (since gevent 1.2a2) they used “DummyThread-12345”. See issue #1659.

  • Fix compatibility with dnspython 2.


    This currently means that it can be imported. But it cannot yet be used. gevent has a pinned dependency on dnspython < 2 for now.

    See issue #1661.

20.6.2 (2020-06-16)#


  • It is now possible to build and use the embedded libuv on a Cygwin platform.

    Note that Cygwin is not an officially supported platform of upstream libuv and is not tested by gevent, so the actual working status is unknown, and this may bitrot in future releases.

    Thanks to berkakinci for the patch. See issue #1645.


  • Relax the version constraint for psutil on PyPy.

    Previously it was pinned to 5.6.3 for PyPy2, except for on Windows, where it was excluded. It is now treated the same as CPython again. See issue #1643.

20.6.1 (2020-06-10)#


  • gevent’s CI is now tested on Ubuntu 18.04 (Bionic), an upgrade from 16.04 (Xenial). See issue #1623.


  • On Python 2, the dnspython resolver can be used without having selectors2 installed. Previously, an ImportError would be raised. See issue #1641.

  • Python 3 gevent.ssl.SSLSocket objects no longer attempt to catch ConnectionResetError and treat it the same as an SSLError with SSL_ERROR_EOF (typically by suppressing it).

    This was a difference from the way the standard library behaved (which is to raise the exception). It was added to gevent during early testing of OpenSSL 1.1 and TLS 1.3. See issue #1637.

20.6.0 (2020-06-06)#


  • Add gevent.selectors containing GeventSelector. This selector implementation uses gevent details to attempt to reduce overhead when polling many file descriptors, only some of which become ready at any given time.

    This is monkey-patched as selectors.DefaultSelector by default.

    This is available on Python 2 if the selectors2 backport is installed. (This backport is installed automatically using the recommended extra.) When monkey-patching, selectors is made available as an alias to this module. See issue #1532.

  • Depend on greenlet >= 0.4.16. This is required for CPython 3.9 and 3.10a0. See issue #1627.

  • Add support for Python 3.9.

    No binary wheels are available yet, however. See issue #1628.


  • gevent.socket.create_connection and gevent.socket.socket.connect no longer ignore IPv6 scope IDs.

    Any IP address (IPv4 or IPv6) is no longer subject to an extra call to getaddrinfo. Depending on the resolver in use, this is likely to change the number and order of greenlet switches. (On Windows, in particular test cases when there are no other greenlets running, it has been observed to lead to LoopExit in scenarios that didn’t produce that before.) See issue #1634.

20.5.2 (2020-05-28)#


  • Forking a process that had use the threadpool to run tasks that created their own hub would fail to clean up the threadpool by raising greenlet.error. See issue #1631.

20.5.1 (2020-05-26)#


  • Waiters on Event and Semaphore objects that call wait() or acquire(), respectively, that find the Event already set, or the Semaphore available, no longer “cut in line” and run before any previously scheduled greenlets. They now run in the order in which they arrived, just as waiters that had to block in those methods do. See issue #1520.

  • Update tested PyPy version from 7.3.0 to 7.3.1 on Linux. See issue #1569.

  • Make zope.interface, zope.event and (by extension) setuptools required dependencies. The events install extra now does nothing and will be removed in 2021. See issue #1619.

  • Update bundled libuv from 1.36.0 to 1.38.0. See issue #1621.

  • Update bundled c-ares from 1.16.0 to 1.16.1.

    On macOS, stop trying to adjust c-ares headers to make them universal. See issue #1624.


  • Make gevent locks that are monkey-patched usually work across native threads as well as across greenlets within a single thread. Locks that are only used in a single thread do not take a performance hit. While cross-thread locking is relatively expensive, and not a recommended programming pattern, it can happen unwittingly, for example when using the threadpool and logging.

    Before, cross-thread lock uses might succeed, or, if the lock was contended, raise greenlet.error. Now, in the contended case, if the lock has been acquired by the main thread at least once, it should correctly block in any thread, cooperating with the event loop of both threads. In certain (hopefully rare) cases, it might be possible for contended case to raise LoopExit when previously it would have raised greenlet.error; if these cases are a practical concern, please open an issue.

    Also, the underlying Semaphore always behaves in an atomic fashion (as if the GIL was not released) when PURE_PYTHON is set. Previously, it only correctly did so on PyPy. See issue #1437.

  • Rename gevent’s C accelerator extension modules using a prefix to avoid clashing with other C extensions. See issue #1480.

  • Using gevent.wait on an Event more than once, when that Event is already set, could previously raise an AssertionError.

    As part of this, exceptions raised in the main greenlet will now include a more complete traceback from the failing greenlet. See issue #1540.

  • Avoid closing the same Python libuv watcher IO object twice. Under some circumstances (only seen on Windows), that could lead to program crashes. See issue #1587.

  • gevent can now be built using Cython 3.0a5 and newer. The PyPI distribution uses this version.

    The libev extension was incompatible with this. As part of this, certain internal, undocumented names have been changed.

    (Technically, gevent can be built with Cython 3.0a2 and above. However, up through 3.0a4 compiling with Cython 3 results in gevent’s test for memory leaks failing. See this Cython issue.) See issue #1599.

  • Destroying a hub after joining it didn’t necessarily clean up all resources associated with the hub, especially if the hub had been created in a secondary thread that was exiting. The hub and its parent greenlet could be kept alive.

    Now, destroying a hub drops the reference to the hub and ensures it cannot be switched to again. (Though using a new blocking API call may still create a new hub.)

    Joining a hub also cleans up some (small) memory resources that might have stuck around for longer before as well. See issue #1601.

  • Fix some potential crashes under libuv when using gevent.signal_handler. The crashes were seen running the test suite and were non-deterministic. See issue #1606.

20.5.0 (2020-05-01)#


  • Update bundled c-ares to version 1.16.0. Changes. See issue #1588.

  • Update all the bundled config.guess and config.sub scripts. See issue #1589.

  • Update bundled libuv from 1.34.0 to 1.36.0. See issue #1597.


  • Use ares_getaddrinfo instead of a manual lookup.

    This requires c-ares 1.16.0.

    Note that this may change the results, in particular their order.

    As part of this, certain parts of the c-ares extension were adapted to use modern Cython idioms.

    A few minor errors and discrepancies were fixed as well, such as gethostbyaddr('localhost') working on Python 3 and failing on Python 2. The DNSpython resolver now raises the expected TypeError in more cases instead of an AttributeError. See issue #1012.

  • The c-ares and DNSPython resolvers now raise exceptions much more consistently with the standard resolver. Types and errnos are substantially more likely to match what the standard library produces.

    Depending on the system and configuration, results may not match exactly, at least with DNSPython. There are still some rare cases where the system resolver can raise herror but DNSPython will raise gaierror or vice versa. There doesn’t seem to be a deterministic way to account for this. On PyPy, getnameinfo can produce results when CPython raises socket.error, and gevent’s DNSPython resolver also raises socket.error.

    In addition, several other small discrepancies were addressed, including handling of localhost and broadcast host names.


    This has been tested on Linux (CentOS and Ubuntu), macOS, and Windows. It hasn’t been tested on other platforms, so results are unknown for them. The c-ares support, in particular, is using some additional socket functions and defines. Please let the maintainers know if this introduces issues.

    See issue #1459.

20.04.0 (2020-04-22)#


  • Let CI (Travis and Appveyor) build and upload release wheels for Windows, macOS and manylinux. As part of this, (a subset of) gevent’s tests can run if the standard library’s module has been stripped. See issue #1555.

  • Update tested PyPy version from 7.2.0 on Windows to 7.3.1. See issue #1569.


  • Fix a spurious warning about watchers and resource leaks on libuv on Windows. Reported by Stéphane Rainville. See issue #1564.

  • Make monkey-patching properly remove select.epoll and select.kqueue. Reported by Kirill Smelkov. See issue #1570.

  • Make it possible to monkey-patch contextvars before Python 3.7 if a non-standard backport that uses the same name as the standard library does is installed. Previously this would raise an error. Reported by Simon Davy. See issue #1572.

  • Fix destroying the libuv default loop and then using the default loop again. See issue #1580.

  • libuv loops that have watched children can now exit. Previously, the SIGCHLD watcher kept the loop alive even if there were no longer any watched children. See issue #1581.

Deprecations and Removals#

  • PyPy no longer uses the Python allocation functions for libuv and libev allocations. See issue #1569.


Older Releases#

For full information on older versions, see Information About Older Releases.

Older change logs, without context.