raspiのpythonを3.8にする

importlib.metadata
が3.8から使えるということでraspiのバージョンを上げました。

3.7.3 -> 3.8

Raspberry Pi OS (Raspbian Buster)は、デフォルトでPython 3.8は提供されていない（？）
Python 3.8を手動でインストールする。

$ sudo apt update
$ sudo apt install -y \
    build-essential \
    libssl-dev \
    zlib1g-dev \
    libncurses5-dev \
    libncursesw5-dev \
    libreadline-dev \
    libsqlite3-dev \
    libgdbm-dev \
    libdb5.3-dev \
    libbz2-dev \
    libexpat1-dev \
    liblzma-dev \
    tk-dev \
    libffi-dev \
    libgdbm-compat-dev \
    wget


$ cd /usr/src
$ sudo wget https://www.python.org/ftp/python/3.8.0/Python-3.8.0.tgz
$ sudo tar xzf Python-3.8.0.tgz

$ python3.8 --version
->
Python 3.8.0

めんどくさいのでシンボリックリンクを作成

$ sudo ln -sf /usr/local/bin/python3.8 /usr/bin/python
$ ls -l /usr/local/bin/python3.8 /usr/bin/python
lrwxrwxrwx 1 root root       24  7月  3 21:39 /usr/bin/python -> /usr/local/bin/python3.8
-rwxr-xr-x 1 root root 15283956  7月  3 20:43 /usr/local/bin/python3.8

$ python --version
Python 3.8.0

$ cd [ソースがある場所へ]
$ python -m venv .venv
$ source .venv/bin/activate

$ pip install gpiozero

->
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Collecting gpiozero
  Using cached https://files.pythonhosted.org/packages/b3/b5/64b461f496134218886a18cbfa40def2b9b1c152c10c71efa992f07952e0/gpiozero-2.0-py3-none-any.whl
Collecting colorzero (from gpiozero)
  Using cached https://files.pythonhosted.org/packages/7e/a6/ddd0f130e44a7593ac6c55aa93f6e256d2270fd88e9d1b64ab7f22ab8fde/colorzero-2.0-py2.py3-none-any.whl
Requirement already satisfied: setuptools in /home/pi/.venv/lib/python3.7/site-packages (from colorzero->gpiozero) (40.8.0)
Installing collected packages: colorzero, gpiozero
Successfully installed colorzero-2.0 gpiozero-2.0

成功