title: Python3 reporting wrong version
body: <p>I have a Raspberry Pi 4 running Raspbian 10. I've been trying to update the version of Python 3 that is installed so I can run Home Assistant which required 3.9.0, but it's all gone a bit pear shaped. The Pi runs a couple of other things so I'm doing a manual install instead of using the bundled Home Assistant OS.</p>
  <p>I did have Python 3.7.3 installed. I then installed 3.9.0 apparently successfully. However running <code>python3 --version</code>
  was still reporting 3.7.3. After a bit of Googling I managed to get the
  <code>python --version</code>
  command to show 3.9.0. But python3 stubbornly continues to report 3.7.3. How do I get
  <code>python3 --version</code>
  to report 3.9.0 instead of 3.7.3?</p>
  <p>I've also tried installing Python 3.9.13, but that errors out so I've abandoned that for now.</p>
  <p>I have run sudo apt update and sudo apt upgrade, so everything is as up to date as it can be.</p>
  <p>BTW, I know very little about Linux, so I know I could have easily screwed things up.</p>