How can I install the Python library 'gevent' on Mac OS X Lion

After a while, I realized that the paths for the CFLAGS variable mentioned above works when installing libevent from port, but not from brew. The following worked for me (on OSX Mavericks):

$ brew install libevent
$ export CFLAGS="-I /usr/local/Cellar/libevent/2.0.21/include -L /usr/local/Cellar/libevent/2.0.21/lib"
$ pip install gevent

Don't post the entire thing! That's too much! 90% of the time, the first error is enough...

gevent/libevent.h:9:19: error: event.h: No such file or directory

This means that the library which provides the event.h header is not installed. The library is called libevent (website).

In general, compilation errors like these are a flaw in the build scripts. The build script should give an error message that libevent is not installed, and it is a bug that it did not do so.

To get libevent from MacPorts and then manually tell compiler with CFLAGS environment variable where to find event.h and libevent while running pip.

sudo port install libevent
CFLAGS="-I /opt/local/include -L /opt/local/lib" pip install gevent

You can also use homebrew for installing libevent : brew install libevent
(from David Wolever's comment)

CFLAGS='-std=c99' pip install gevent

See in: Can't install gevent OSX 10.11

on OS X 10.11, clang uses c11 as the default, so just turn it back to c99.