Create your own AI app with GPT-4

4 min readNov 9, 2023

Build custom apps with the GPT-4 AI model. Learn how to create an Open AI API key and then call the API from within a python application.

GPT-4 Beginner Series:

- Prerequisites
- Github Repo
- Create an Open AI API key
- Add your API key to an environment variable
- Use your API key in a python app
- Pricing and Usage
- What's next?

Prerequisites

Basic knowledge of the terminal / command prompt (how to set environment variables on your system and run programs)
To complete this tutorial, you must have python installed: https://www.python.org/downloads/

You will need a text editor to write code. I use VSCode: https://code.visualstudio.com/download

Github Repo

All code for this tutorial is available on Github: https://github.com/ATLucas/aidev/tree/main/tutorials/openai_api_basics

Create an Open AI API key

Navigate in a browser to https://openai.com/
Click Log in

Select API

Select API Keys from the left side menu

Click Create new secret key

Give your key a name and click Create secret key

Copy your key somewhere safe and click Done

Add your API key to an environment variable

Open a terminal
Open/create your .bash_profile:

$ nano ~/.bash_profile

Add this line to the file:

export OPENAI_API_KEY=[ENTER YOUR KEY HERE]

Type CTRL+X to exit the nano editor and save the file by typing ENTER
Source your .bash_profile with the new env var added:

$ source ~/.bash_profile

Verify the env var is set:

$ echo $OPENAI_API_KEY
[YOUR API KEY]

Use your API key in a python app

Install the openai python module

$ python3 -m pip install openai

Clone the repo containing the tutorial code

$ git clone git@github.com:ATLucas/aidev.git

Change to the tutorial directory

$ cd aidev/tutorials/openai_api_basics

Run the command line app

$ python3 main.py

(Had to use GPT-3-turbo for this example due to Open AI outages after dev day)
The code for communicating with ChatGPT in this tutorial was based on the Open AI API python quickstart: https://platform.openai.com/docs/quickstart?context=python

Pricing and Usage

While the cost to run this app is small, know that you will be charged for usage according to the API pricing guide (likely just pennies for a short conversation). GPT-4 costs quite a bit more than GPT-3-turbo. It can be 10 to 30 times as much, depending on the model you choose.
Pricing guide: https://openai.com/pricing
Check your API usage: https://platform.openai.com/usage

What’s next?

Try-out different models by adjusting the MODELS variable at the top of the python script. Model names can be found here: https://platform.openai.com/docs/models/continuous-model-upgrades
Note that as of the writing of this article, the GPT-4 models were temporarily removed, likely due to the Open AI servers going down in the aftermath of dev day.
Try modifying the SYSTEM_PROMPT variable and see how it impacts your conversation. For example, tell GPT that it should act like your favorite movie character.

In the next article, we’ll take a look at the new assistants API for creating GPT-4-turbo agents…assuming Open AI can get GPT-4 back up-and-running sometime soon…

UPDATE

Turns-out I just didn’t have payments setup properly in the Open AI account I was using, and that’s why I didn’t have access to the GPT-4 models anymore.

In any case, go to Settings in the left side panel, click to drop-down and select Billing. Then add a payment method and fund your account. The GPT-4 model will be immediately available, both in the Open AI platform playground and via the API itself. If you have a Plus account, you should also be able to use the GPT-4 turbo model preview.