https://docs.python.org/3/installing/index.html

jinia@jin:~$ python3 -m pip install nympy
/usr/bin/python3: No module named pip
jinia@jin:~$ python3 -m ensurepip --default-pip
/usr/bin/python3: No module named ensurepip
jinia@jin:~$ python -m ensurepip --default-pip
ensurepip is disabled in Debian/Ubuntu for the system python.

Python modules For the system python are usually handled by dpkg and apt-get.

    apt-get install python-<module name>

Install the python-pip package to use pip itself.  Using pip together
with the system python might have unexpected results for any system installed
module, so use it on your own risk, or make sure to only use it in virtual
environments.

jinia@jin:~$