PIP install unable to find ffi.h even though it recognizes libffi

You need to install the development package as well.

libffi-dev on Debian/Ubuntu, libffi-devel on Redhat/Centos/Fedora.

To add to mhawke's answer, usually the Debian/Ubuntu based systems are "-dev" rather than "-devel" for RPM based systems

So, for Ubuntu it will be apt-get install libffi libffi-dev

RHEL, CentOS, Fedora (up to v22) yum install libffi libffi-devel

Fedora 23+ dnf install libffi libffi-devel

OSX/MacOS (assuming homebrew is installed) brew install libffi

python linux pip

You can use CFLAGS (and LDFLAGS or various other compiler and linker options) in front of the pip command (ditto for setup.py):

Something similar to the following should work:

CFLAGS=-I/usr/include/libffi/include pip install pyOpenSSL

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