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

Question

I have installed libffi on my Linux server as well as correctly set the PKG_CONFIG_PATH environment variable to the correct directory, as pip

Answer 1

pip packages usually don't use pkg-config. Therefore, you should set CFLAGS and LDFLAGS manually:

CFLAGS=$(pkg-config --cflags libffi) LDFLAGS=$(pkg-config --libs libffi) pip install pyOpenSSL

Answer 2

You need to install the development package as well.

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