# gevent

# Installation and Requirements

## Supported Platforms

gevent 1.3 runs on Python 2.7 and Python 3. Releases 3.4, 3.5 and 3.6 of Python 3 are supported. (Users of older versions of Python 2 need to install gevent 1.0.x (2.5), 1.1.x (2.6) or 1.2.x (<=2.7.8); gevent 1.2 can be installed on Python 3.3.) gevent requires the greenlet library and will install the cffi library by default on Windows.

gevent 1.3 also runs on PyPy 5.5 and above, although 5.9 or above is strongly recommended. On PyPy, there are no external dependencies.

gevent is tested on Windows, OS X, and Linux, and should run on most other Unix-like operating systems (e.g., FreeBSD, Solaris, etc.)

Note

On Windows using the libev backend, gevent is limited to a maximum of 1024 open sockets due to limitations in libev. This limitation should not exist with the default libuv backend.

## Installation

Note

This section is about installing released versions of gevent as distributed on the Python Package Index

gevent and greenlet can both be installed with pip, e.g., `pip install gevent`. Installation using buildout is also supported.

On Windows, OS X, and Linux, both gevent and greenlet are distributed as binary wheels.

Tip

You need Pip 8.0 or later, or buildout 2.10.0 to install the binary wheels.

Tip

On Linux, you’ll need to install gevent from source if you wish to use the libuv loop implementation. This is because the manylinux1 specification for the distributed wheels does not support libuv. The cffi library must be installed at build time.

### Installing From Source

If you are unable to use the binary wheels (for platforms where no pre-built wheels are available or if wheel installation is disabled, e.g., for libuv support on Linux), here are some things you need to know.

- You can install gevent from source with `pip install --no-binary gevent gevent`.
- You’ll need a working C compiler that can build Python extensions. On some platforms, you may need to install Python development packages.
- Installing from source requires `setuptools`. This is installed automatically in virtual environments and by buildout. However, gevent uses PEP 496 environment markers in `setup.py`. Consequently, you’ll need a version of setuptools newer than 25 (mid 2016) to install gevent from source; a version that’s too old will produce a `ValueError`. Older versions of pipenv may also have issues installing gevent for this reason.
- To build the libuv backend (which is required on Windows and optional elsewhere), or the CFFI-based libev backend, you must install cffi before attempting to install gevent on CPython (on PyPy this step is not necessary).

### Common Installation Issues

The following are some common installation problems and solutions for those compiling gevent from source.

- Some Linux distributions are now mounting their temporary directories with the `noexec` option. This can cause a standard `pip install gevent` to fail with an error like `cannot run C compiled programs`. One fix is to mount the temporary directory without that option. Another may be to use the `--build` option to `pip install` to specify another directory. See issue #570 and issue #612 for examples.
- Also check for conflicts with environment variables like `CFLAGS`. For example, see Library Updates.
- Users of a recent SmartOS release may need to customize the `CPPFLAGS` (the environment variable containing the default options for the C preprocessor) if they are using the libev shipped with gevent. See Operating Systems for more information.
- If you see `ValueError: ("Expected ',' or end-of-list in", "cffi >= 1.11.5 ; sys_platform == 'win32' and platform_python_implementation == 'CPython'", 'at', " ; sys_platform == 'win32' and platform_python_implementation == 'CPython'")`, the version of setuptools is too old. Install a more recent version of setuptools.

## Extra Dependencies

gevent has no runtime dependencies outside the standard library, greenlet and (on some platforms) cffi. However, there are a number of additional libraries that extend gevent’s functionality and will be used if they are available.

The psutil library is needed to monitor memory usage.

zope.event is highly recommended for configurable event support; it can be installed with the `events` extra, e.g., `pip install gevent[events]`.

dnspython is required for the new pure-Python resolver, and on Python 2, so is idna. They can be installed with the `dnspython` extra.

## Development

To install the latest development version:

    pip install setuptools cffi 'cython>=0.28' git+git://github.com/gevent/gevent.git#egg=gevent

Note

You will not be able to run gevent’s test suite using that method.

To hack on gevent (using a virtualenv):

    $ git clone https://github.com/gevent/gevent.git
    $ cd gevent
    $ virtualenv env
    $ source env/bin/activate
    (env) $ pip install -r dev-requirements.txt

Note

The notes above about installing from source apply here as well. The `dev-requirements.txt` file takes care of the library prerequisites (CFFI, Cython), but having a working C compiler that can create Python extensions is up to you.

### Running Tests

There are a few different ways to run the tests. To simply run the tests on one version of Python during development, begin with the above instructions to install gevent in a virtual environment and then run:

    (env) $ python -mgevent.tests

Before submitting a pull request, it’s a good idea to run the tests across all supported versions of Python, and to check the code quality using prospector. This is what is done on Travis CI. Locally it can be done using tox:

    pip install tox
    tox

The testrunner accepts a `--coverage` argument to enable code coverage metrics through the coverage.py package. That would go something like this:

    python -m gevent.tests --coverage
    coverage combine
    coverage html -i
    <open htmlcov/index.html>

### Continuous integration

A test suite is run for every push and pull request submitted. Travis CI is used to test on Linux, and AppVeyor runs the builds on Windows.

Builds on Travis CI automatically submit updates to coveralls.io to monitor test coverage.

Note

On Debian, you will probably need `libpythonX.Y-testsuite` installed to run all the tests.

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