Script for installing python-mapnik on MacOS Catalina with Homebrew

build-python-mapnik-osx.sh

#!/bin/bash

# note: boost needs to be >= 1.73, make sure boost@1.73 is linked too
brew install boost boost-python3 sqlite gdal cairo python@3.8
brew upgrade boost boost-python3 sqlite gdal cairo python@3.8
brew link boost

# We're build a custom mapnik 4, uninstall the stale 3.x version in homebrew:
brew uninstall mapnik

mkdir build-python-mapnik
cd build-python-mapnik

# Build Mapnik from master
git clone https://github.com/mapnik/mapnik
cd mapnik
git submodule update --init
set -e
# be explicit: python3 will result in sconstruct build failure
PYTHON=python2 ./configure SQLITE_INCLUDES=/usr/local/opt/sqlite3/include
JOBS=8 make
make install
set +e
cd ..

git clone https://github.com/mapnik/python-mapnik
cd python-mapnik
set -e
BOOST_PYTHON_LIB=boost_python38 python3 setup.py install
#!/bin/bash

# note: boost needs to be >= 1.73, make sure boost@1.73 is linked too
brew install boost boost-python3 sqlite gdal cairo python@3.8
brew upgrade boost boost-python3 sqlite gdal cairo python@3.8
brew link boost

# We're build a custom mapnik 4, uninstall the stale 3.x version in homebrew:
brew uninstall mapnik

mkdir build-python-mapnik
cd build-python-mapnik

# Build Mapnik from master
git clone https://github.com/mapnik/mapnik
cd mapnik
git submodule update --init
set -e
# be explicit: python3 will result in sconstruct build failure
PYTHON=python2 ./configure SQLITE_INCLUDES=/usr/local/opt/sqlite3/include
JOBS=8 make
make install
set +e
cd ..

git clone https://github.com/mapnik/python-mapnik
cd python-mapnik
set -e
BOOST_PYTHON_LIB=boost_python38 python3 setup.py install
cd ../..

python3 -c "import mapnik ; print(dir(mapnik))"

Updated your script for MacOs 10.15.7; python 3.9 is required for boost-python3

#!/bin/bash

# note: boost needs to be >= 1.73, make sure boost@1.73 is linked too

brew install boost boost-python3 sqlite gdal cairo python@3.9
brew upgrade boost boost-python3 sqlite gdal cairo python@3.9
brew link boost

# We're build a custom mapnik 4, uninstall the stale 3.x version in homebrew:
brew uninstall mapnik

mkdir build-python-mapnik
cd build-python-mapnik

# Build Mapnik from master
git clone https://github.com/mapnik/mapnik
cd mapnik
git submodule update --init
set -e
# be explicit: python3 will result in sconstruct build failure
PYTHON=python2 ./configure SQLITE_INCLUDES=/usr/local/opt/sqlite3/include

JOBS=8 make
make install
set +e
cd ..

git clone https://github.com/mapnik/python-mapnik
cd python-mapnik
set -e
BOOST_PYTHON_LIB=boost_python39 /usr/local/Cellar/python@3.9/3.9.0/bin/python3 setup.py install

cd ../..

/usr/local/Cellar/python@3.9/3.9.0/bin/python3 -c "import mapnik ; print(dir(mapnik))"

I found that as is the build didn't pick up some the options - GDAL and PROJ. I fixed this by adding to the configure line as follows:

PYTHON=python2 ./configure SQLITE_INCLUDES=/usr/local/opt/sqlite3/include GDAL_CONFIG=/usr/local/opt/gdal/bin/gdal-config PROJ_LIBS=/usr/local/lib PROJ_INCLUDES=/usr/local/include CUSTOM_DEFINES='-DACCEPT_USE_OF_DEPRECATED_PROJ_API_H=1'

The last one allows use of newer versions of PROJ than PROJ 4.