how to write requirements.txt for python code example

Example 1: command to make requirements.txt

pip freeze > requirements.txt

Example 2: python requirements.txt

pip freeze #view requirements to be created (best done in virtual env)
pip freeze > requirements.txt #create requirements.txt (best done in virtual env)
pip install -r requirements.txt #install requirements.txt (best done in virtual env)

Example 3: 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