DeepSeek in the terminal

A step-by-step setup for running an AI coding assistant from your command line. Follow it top to bottom — you can copy and paste every command.

1Open your terminal

The terminal is a window where you type commands.

• Windows Press the Windows key, type powershell, press Enter. A blue-ish window opens — that's it.
• Mac Press Cmd + Space, type terminal, press Enter.

Everything below is typed into this window. Type one line, press Enter, wait for it to finish, then do the next.

2Make sure you have Python

Type this and press Enter:

Windows:  python --version
Mac:      python3 --version

If it prints a number like 3.11, you're set — skip to step 3. If it says "not found," install it from python.org/downloads. Windows during install, tick the box "Add Python to PATH". Then close the terminal, open it again, and check the version once more.

3Install Aider (the assistant)

Aider is the tool that puts the AI in your terminal. Install it once:

Windows:  pip install aider-chat
Mac:      pip3 install aider-chat

4Get your DeepSeek key

• Go to platform.deepseek.com and sign up.
• Create an API key and copy it somewhere safe for a minute.
• Add $5–10 of balance — that's enough for a whole month.

5Make a folder and save your key in it

Make a folder to work in and go into it:

mkdir practice
cd practice

Inside it, create a file named .env (the dot is part of the name) containing your key. Aider reads this file automatically, so you never type the key again.

# .env  —  one line, paste your real key after the =
DEEPSEEK_API_KEY=your-deepseek-key-here

Easiest way to create it: type notepad .env on Windows (or open -e .env on Mac), paste the line, save.

6Start it

aider --model deepseek/deepseek-chat

A chat opens right in the terminal. Type what you want in plain English and it writes and edits code for you. The handful of commands you'll use:

• /add file.py — let it see and edit a file
• /run python file.py — run something and show it the result
• /undo — take back its last change · /help — everything else
• Type /exit to leave.

7Pulling company data (Harmonic)

Once Aider is running you don't have to write API code by hand — just ask. First, Mark will give you the Harmonic key privately; add it to the same .env file on its own line:

HARMONIC_API_KEY=the-key-mark-gives-you

Then in Aider, ask in plain words, for example:

"Write a Python script that reads HARMONIC_API_KEY from the .env file,
 looks up a company by its website on the Harmonic API
 (POST https://api.harmonic.ai/companies?website_url=... , header  apikey: KEY),
 and prints the company name, funding stage, and headcount. Then run it on stripe.com."

Aider writes it, runs it, and shows you the result. That's the whole loop — and it's how you'll learn every other API too.

8Two rules that don't bend

• Your keys are private — never share them, never paste them into a chat, never post them online.