Method 1:
https://github.com/pyenv/pyenv-virtualenv
pyenv virtualenv 3.9.9 deeplearn23
pyenv activate deeplearn23
pyenv uninstall 3.9.9/envs/deeplearn23

Method 2
virtualenv <my_env_name> to create a new environment
source <my_env_name>/bin/activate to activate the new environment
pip install -r requirements.txt to install the requirements in the current environment
#Remember to change interpreter path afterward