how to generate requirements.txt python from python code example

Example: how to create a requirements.txt python

# Exit the current venv
(shiny_new_env)$ conda deactivate
# Spin up a new one
$ conda create -n env_2 python=3.4
# Activate it
$ conda activate env_2
# Install from our fancy new file
(env_2)$ pip install -r requirements.txt