Pip for Python 3.8

sudo apt install python3.8
sudo apt install python3.8-distutils

wget https://bootstrap.pypa.io/get-pip.py
sudo python3.8 get-pip.py

If you installed Python3.8 using apt, the pip documentation advises against using the get-pip.py script:

Be cautious if you are using a Python install that is managed by your operating system or another package manager. get-pip.py does not coordinate with those tools, and may leave your system in an inconsistent state.

The same page suggests running:

python3.8 -m pip --version

to determine if pip is already installed. I installed Python 3.8 on an Ubuntu18 machine using apt install python3.8, and I verified with the command above that it includes pip. It appears that Ubuntu package doesn't install a pip command that you can run directly. But you can run it using the python3.8 binary directly instead, anywhere you would have used pip:

python3.8 -m pip install [package]

you can try updating line #1 from /usr/bin/pip3 to #!/usr/bin/python3.8 as below

#!/usr/bin/python3.8
# GENERATED BY DEBIAN

import sys

# Run the main entry point, similarly to how setuptools does it, but because
# we didn't install the actual entry point from setup.py, don't use the
# pkg_resources API.
from pip import main
if __name__ == '__main__':
    sys.exit(main())

What I used to install pip according to the current version of default python is:

 sudo apt-get install python-pip

Use the ensurepip module:

python3.8 -m ensurepip --upgrade