how to get requirements .txt

$ env1/bin/pip freeze > requirements.txt
$ env2/bin/pip install -r requirements.txt

# 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

pip freeze > requirements.txt