I do pip3 install ...
It makes clear, that the install is for python3.
I hate it, if the librays start to mix.
My programms, in ex Firefox still using Python2 code. But I use v3 to coding. All manual pip installs are only for Python3.
Maybe think for your self, if you need a virtual enviroment for a project. All librarys are containered and do not cause conflicts.