title: Switching Python version installed by Homebrew
body: <p>I have Python 3.8 and 3.9 installed via Homebrew:</p>
  <pre><code>~ brew list | grep python
  python@3.8
  python@3.9
  </code></pre>
  <p>I want to use Python 3.9 as my default one with <code>python3</code> command. I tried the following:</p>
  <pre><code>~ brew switch python 3.9
  Error: python does not have a version &quot;3.9&quot; in the Cellar.
  python's installed versions: 3.8.6
  </code></pre>
  <p>I tried to uninstall Python and reinstall it, but it's used by other packages:</p>
  <pre><code>~ brew uninstall python
  Error: Refusing to uninstall /usr/local/Cellar/python@3.8/3.8.6
  because it is required by glib and php, which are currently installed.
  You can override this and force removal with:
    brew uninstall --ignore-dependencies python
  </code></pre>
  <p>How can I use Python 3.9?</p>