My Python installer using pyenv

install-pythons.sh

#!/usr/bin/env bash
set -e

versions=(
  2.7.18
  3.7.9
  3.8.7
  3.9.1
  pypy3.6-7.3.1
)

version() {
  # shellcheck disable=SC2046,SC2183
  printf "%03d%03d%03d" $(echo "$1" | tr '.' ' ')
}

hline() {
  printf -- "-%.0s" $(seq "$(tput cols)")
}

if ! command -v pyenv > /dev/null; then
  echo "pyenv seems uninstall" > /dev/stderr
  exit 1
fi

if command -v xcrun > /dev/null; then
  CFLAGS="-I$(xcrun --show-sdk-path)/usr/include $CFLAGS"
  export CFLAGS
fi

if command -v brew > /dev/null; then
  # Older Python versions cannot be built with OpenSSL 1.1
  brew install rbenv/tap/openssl@1.0
  brew unlink openssl@1.0

  CFLAGS="-I$(brew --prefix readline)/include $CFLAGS"
  OPENSSL10_CFLAGS="-I$(brew --prefix openssl@1.0)/include $CFLAGS"
  CFLAGS="-I$(brew --prefix openssl@1.1)/include $CFLAGS"
  LDFLAGS="-L$(brew --prefix readline)/lib $LDFLAGS"
  OPENSSL10_LDFLAGS="-L$(brew --prefix openssl@1.0)/lib $LDFLAGS"
  LDFLAGS="-L$(brew --prefix openssl@1.1)/lib $LDFLAGS"
  OPENSSL10_CONFIGURE_OPTS="--with-openssl=$(brew --prefix openssl@1.0)"
  CONFIGURE_OPTS="--with-openssl=$(brew --prefix openssl@1.1)"
  export CFLAGS
  export LDFLAGS
  export CONFIGURE_OPTS
fi

# Sort versions in ascending order
readarray -t versions < <(printf '%s\n' "${versions[@]}" | sort -rV)
for ver in "${versions[@]}"; do
  if [[ "$ver" = 3.* ]]; then
    py3_latest="${py3_latest:-$ver}"
  elif [[ "$ver" = 2.* ]]; then
    py2_latest="${py2_latest:-$ver}"
  fi
  if [[ "$py2_latest" != "" && "$py3_latest" != "" ]]; then
    break
  fi
done

# Each latest version in major versions (2 and 3) go first
i=$((2))
for ver in "${versions[@]}"; do
  if [[ "$ver" = "$py3_latest" || "$ver" = "$py2_latest" ]]; then
    continue
  fi
  versions[$i]="$ver"
  ((i++))
done
versions[0]="$py2_latest"
versions[1]="$py3_latest"

for (( i=${#versions[@]}-1; i>=0; i-- )); do
  {
    hline
    echo "${versions[i]}"
    hline
  } > /dev/stderr
  if ! [[ "${versions[i]}" = pypy* ]] && { \
       [ "$(version "${versions[i]}")" -lt "$(version 2.7.0)" ] || \
       [ "$(version "${versions[i]}")" -ge "$(version 3.0.0)" ] && \
       [ "$(version "${versions[i]}")" -lt "$(version 3.6.0)" ]
    }; then
    # Older Python versions that should be built with OpenSSL 1.0 (not 1.1)
    brew unlink openssl@1.1
    CFLAGS="${OPENSSL10_CFLAGS:-$CFLAGS}" \
    LDFLAGS="${OPENSSL10_LDFLAGS:-$LDFLAGS}" \
    CONFIGURE_OPTS="${OPENSSL10_CONFIGURE_OPTS:-$CONFIGURE_OPTS}" \
    PYTHON_BUILD_HOMEBREW_OPENSSL_FORMULA=openssl@1.0 \
    pyenv install -f "${versions[i]}"
    brew unlink openssl@1.0
    brew link openssl@1.1
  else
    pyenv install -f "${versions[i]}"
  fi
done
pyenv global "${versions[@]}"