1. vim ~/.bashrc
2. Press i on your keyboard to enter insert mode in vim.
3. Write export KEY=VALUE somewhere in the end, anywhere is fine really
4. Press esc(escape key) to enter command mode, now type :wq - this will save and quit.
5. Now, in Python, write the following:

import os
key = os.getenv('<KEY_NAME>')

6. Now use key as needed