Virtual environments, or venv, create a containerized environment of running your Python applications. You install all the Python packages you use for a specific program in one virtual environment.
When you simply run python --version in your terminal, you get the version that is installed on your computer. That is mostly likely sourced from your /usr/local/bin directory.
Check where pip3 is sourced from and check which version are you running.
which pip3
pip3 --version
List installed packages on your system.
pip3 list
Create virtual environment with the name of <venv_name> in your current directory.
python3 -m venv <venv_name>
Activate that virtual environment.
source <venv_name>/bin/activate
Print on the screen a list of installed in a specific format for import and export.
pip freeze
Create requirements.txt.
pip freeze > requirements.txt
Deactivate virtual environment and delete it.
deactivate
rm -rf <venv_name>
Install packages into virtual environment from requirements.txt.
pip install -r requirements.txt