Install `numpy` and `scipy` on M1 Mac (Python 3.9 from Homebrew)

mac_m1_create_venv.zsh

#!/bin/zsh
# Creates a virtual environment and installs requirements while taking into account
# the apparent lack of a binary wheel for scipy on M1 Mac.

set -ueo pipefail

if [ "$(uname -m)" != "arm64" ]; then
    echo "WARNING: You should not need this script as you are not running an M1 Mac." > /dev/fd/2
fi

PYTHON="${PYTHON:-python3.9}"
VENV="${1:-venv}"

if [ -d "$VENV" ]; then
    echo "ERROR: $VENV exists. Please rm -rf it to continue." > /dev/fd/2
    exit 1
fi

export OPENBLAS="$(brew --prefix openblas)"
NUMPY="$(fgrep 'numpy==' requirements.txt)"
SCIPY="$(fgrep 'scipy==' requirements.txt)"

if [ ! -f "$OPENBLAS/lib/libopenblas.a" ]; then
    brew install openblas
fi

"$PYTHON" -m venv "$VENV"
source "$VENV/bin/activate"

set -x

pip install -U pip setuptools wheel

# install scipy build requirements
pip install --no-cache --no-use-pep517 pybind11 Cython pythran "$NUMPY"

# install scipy
pip install --no-cache --no-use-pep517 "$SCIPY"
pip install -r requirements.txt