pip vs pip3

[snippsat]

if one does not yet have pip or pip3, how is it initially installed?

sudo apt install python3-pip

You can look at this,there i start from a new Distro.
Had a problem with pip 18.0,so had to do changes in /usr/bin/pip3 to get pip 18.0 to work.
To recover the pip3 binary:

sudo python3 -m pip uninstall pip && sudo apt install python3-pip --reinstall

Working it look like this:

tom@tom-VirtualBox:~$ which pip
/home/tom/.local/bin/pip
tom@tom-VirtualBox:~$ which pip3
/home/tom/.local/bin/pip3

tom@tom-VirtualBox:~$ pip -V
pip 18.0 from /home/tom/.local/lib/python3.6/site-packages/pip (python 3.6)
tom@tom-VirtualBox:~$ pip3 -V
pip 18.0 from /home/tom/.local/lib/python3.6/site-packages/pip (python 3.6)

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