First, you need to install pyenv so you can have multiple version of python in your system. then for projects that does not need packaging, you can use pyenv-virtualenv to setup requirements.txt for project based venv.
Second, you need to install pipx, so it installs some shared tools for the whole system. After setting up pipx (using certain version of python specified by pyenv), pipx reuses the python interpreter on which pipx was installed, so if you upgrade python and got the previous one removed, pipx will fail. it is a good practice to fix the python interpreter for pipx so that when you have your default python changed, your pipx does not break. This is done by export PIPX_DEFAULT_PYTHON="$HOME/.pyenv/versions/x.y.z/bin/python"
Third, for python projects you want to pack up for package releasing, you better install poetry with pipx so that it does the building/packaging for you correctly.
for other commonly used python based tools. pipx would often be a better choice for installation too.