Trouble installing pycairo through pip3

Question

I have been trying to install pycairo with pip3 on MacOs but whenever y try to do so this error appears:

pip3 install pycairo
Collecting pycairo
  Using cached https://files.pythonhosted.org/packages/48/20/5e83af98eb897935bf7dc39455e892ba866feebb9b7c3b392982866f9958/pycairo-1.18.1.tar.gz
Installing collected packages: pycairo
  Running setup.py install for pycairo ... error
    ERROR: Complete output from command /Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 -u -c 'import setuptools, tokenize;__file__='"'"'/private/var/folders/0w/2v91jtp54jl7b4cdqrhk_96h0000gn/T/pip-install-uiqmlfkz/pycairo/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/0w/2v91jtp54jl7b4cdqrhk_96h0000gn/T/pip-record-egwlnpkb/install-record.txt --single-version-externally-managed --compile:
    ERROR: running install
    running build
    running build_py
    creating build
    creating build/lib.macosx-10.9-x86_64-3.7
    creating build/lib.macosx-10.9-x86_64-3.7/cairo
    copying cairo/__init__.py -> build/lib.macosx-10.9-x86_64-3.7/cairo
    copying cairo/__init__.pyi -> build/lib.macosx-10.9-x86_64-3.7/cairo
    copying cairo/py.typed -> build/lib.macosx-10.9-x86_64-3.7/cairo
    running build_ext
    Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    Package 'libffi', required by 'gobject-2.0', not found
    Command '['pkg-config', '--print-errors', '--exists', 'cairo >= 1.13.1']' returned non-zero exit status 1.
    ----------------------------------------
ERROR: Command "/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 -u -c 'import setuptools, tokenize;__file__='"'"'/private/var/folders/0w/2v91jtp54jl7b4cdqrhk_96h0000gn/T/pip-install-uiqmlfkz/pycairo/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/0w/2v91jtp54jl7b4cdqrhk_96h0000gn/T/pip-record-egwlnpkb/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/var/folders/0w/2v91jtp54jl7b4cdqrhk_96h0000gn/T/pip-install-uiqmlfkz/pycairo/

I have installed cairo and pkg-config using brew.

Update, i did set the path of PKG_CONFIG_PATH using the following command

export PKG_CONFIG_PATH=/usr/local/Cellar/libffi/3.2.1/lib/pkgconfig/

And later using pip3 to install pycairo it does the job. The only thing is that even if it is installed now python3 doest not find pycairo.

python3
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 16:52:21) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pycairo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'pycairo'

I have the following installed with brew

brew list
aom         jpeg            p11-kit
atk         lame            pango
cairo           leptonica       pcre
ffmpeg          libass          pixman
flac            libbluray       pkg-config
fontconfig      libevent        python
freetype        libffi          readline
frei0r          libogg          rtmpdump
fribidi         libpng          rubberband
gdbm            libsamplerate       sdl2
gdk-pixbuf      libsndfile      snappy
gettext         libsoxr         speex
ghostscript     libtasn1        sqlite
giflib          libtiff         tesseract
glew            libunistring        theora
glib            libvorbis       unbound
gmp         libvpx          webp
gnutls          little-cms2     x264
graphite2       nettle          x265
gtk+            opencore-amr        xvid
harfbuzz        openjpeg        xz
hicolor-icon-theme  openssl
icu4c           opus

and this is my pip3 list

astroid           2.2.5   
cairocffi         1.0.2   
cffi              1.12.3  
isort             4.3.16  
lazy-object-proxy 1.3.1   
mccabe            0.6.1   
opencv-python     3.4.2.17
pip               19.1    
pycairo           1.18.1  #it seems like it's installed but it doesn't recognize it whenever I try to import it
pycparser         2.19    
pylint            2.3.1   
setuptools        40.8.0  
typed-ast         1.3.1   
wrapt             1.11.1  

Answer 1

Had the same problem.

Solution:

Keep your python3 and libffi installed via brew. Only do this before installing cairo:

export LDFLAGS="-L/usr/local/opt/libffi/lib"
export PKG_CONFIG_PATH="/usr/local/opt/libffi/lib/pkgconfig"

Now go ahead and run pip:

pip3 install --user pycairo

Everything should work after this.

Tested on macOS 10.14.6, python 3.7.4 installed via brew, libffi 3.2.1 installed via brew.

Answer 2

You have the answer right there in the pip3 output:

Package 'libffi', required by 'gobject-2.0', not found

On macOS, brew install libffi should do it.

(Also, of course, installing anything into the system Python, and not inside a virtualenv, is usually a bad idea.)