Ubuntu 20.04 comes with Python 3.8. I cannot uninstall Python 3.8 but I need Python 3.9

I went ahead and installed Python 3.9 from:

sudo add-apt-repository ppa:deadsnakes/ppa

sudo apt install python3.9

How do I install pip for python 3.9?

Installing pip using sudo apt-get install python3-pip does not work for me as it installs pip for python 3.8

Installing pip using python3.9 get-pip.py gives an error:

~/python_tools$ python3.9 get-pip.py 
Traceback (most recent call last):
  File "/home/ubuntu/python_tools/get-pip.py", line 23704, in <module>
    main()
  File "/home/ubuntu/python_tools/get-pip.py", line 198, in main
    bootstrap(tmpdir=tmpdir)
  File "/home/ubuntu/python_tools/get-pip.py", line 82, in bootstrap
    from pip._internal.cli.main import main as pip_entry_point
  File "<frozen zipimport>", line 259, in load_module
  File "/tmp/tmpkwyc8h7j/pip.zip/pip/_internal/cli/main.py", line 10, in <module>
  File "<frozen zipimport>", line 259, in load_module
  File "/tmp/tmpkwyc8h7j/pip.zip/pip/_internal/cli/autocompletion.py", line 9, in <module>
  File "<frozen zipimport>", line 259, in load_module
  File "/tmp/tmpkwyc8h7j/pip.zip/pip/_internal/cli/main_parser.py", line 7, in <module>
  File "<frozen zipimport>", line 259, in load_module
  File "/tmp/tmpkwyc8h7j/pip.zip/pip/_internal/cli/cmdoptions.py", line 18, in <module>
ModuleNotFoundError: No module named 'distutils.util'

You can install pip for python 3.9 the following way:

curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
python3.9 get-pip.py

It is important you use python3.9 instead of just python3, to ensure pip is installed for python 3.9.

If you see any permissions errors, you may need to use

python3.9 get-pip.py --user

If you get an error like No module named 'distutils.util' when you run python3.9 get-pip.py, and you are on a Debian-based Linux distribution, run

sudo apt install python3.9-distutils

and then rerun your get-pip.py command. If you are not on a Debian-based distribution, use the equivalent command for your distribution's package manager.

These instructions are based in part on the official installation instructions provided by the pip maintainers.

This portion of my answer is a bit out of the scope of the question, since the question is specifically for python 3.9. However, for anyone trying to install pip on python 3.6 or older, at the time of writing the file at https://bootstrap.pypa.io/get-pip.py only supports python 3.7 or newer.

The workaround is to instead download from https://bootstrap.pypa.io/pip/<python version>/get-pip.py instead. For example, if you want to install pip for python 3.6, then you can download from https://bootstrap.pypa.io/pip/3.6/get-pip.py, and then follow all of the steps above as usual.