This installs Python under Rosetta and assign it to pyenv to avoid: ModuleNotFoundError: No module named '_ctypes' on M1 Apple Silicon

install_python_rosetta.sh

#!/usr/bin/env bash

# This installs Python under Rosetta and assign it to pyenv.
# This way of installing Python avoids: ModuleNotFoundError: No module named '_ctypes'
# pyenv has to be installed from Github https://laict.medium.com/install-python-on-macos-11-m1-apple-silicon-using-pyenv-12e0729427a9

version=$1

if [ "$#" -ne 1 ]; then
    echo "Illegal number of parameters. Usage:"
    echo "./install_python_rosetta.sh <python-version>"
    exit 1
fi

command -v pyenv >/dev/null 2>&1 || { echo >&2 "Pyenv is required but it's not installed. Aborting."; exit 1; }
command -v arch -x86_64 /usr/local/homebrew/bin/brew >/dev/null 2>&1 || { echo >&2 "arch -x86_64 is required but it's not installed. Aborting."; exit 1; }

alias ibrew='arch -x86_64 /usr/local/homebrew/bin/brew'

major=$(echo "$version" | cut -d. -f1)
minor=$(echo "$version" | cut -d. -f2)
micro=$(echo "$version" | cut -d. -f3)

ibrew install python@"${major}.${minor}"

if [ $? -ne 0 ]
then
    exit 255
fi

# Add `python` executable (symlink to `python3`)
ln -s python3 "$(ibrew --prefix python@"${major}.${minor}")"/bin/python

# Symlink x86 Python into pyenv
ln -s "$(ibrew --prefix python@"${major}.${minor}")" "$HOME"/.pyenv/versions/"${major}.${minor}.${micro}"

# Check
pyenv local "${major}.${minor}.${micro}"
python -V
python -c 'import _ctypes' # works!