OpenAI Function Calling Tutorial: Build a LIVE Weather App with GPT-4 (Step-by-Step Guide)
Learn how to use OpenAI Function Calling to connect ChatGPT to the real world! In this full tutorial, we build a LIVE Weather App using the ChatGPT API and a real-time weather service. You'll learn the 3-step request chain required to turn a user's prompt into a function call, fetch external data, and return a natural language response.
Key Concepts Covered:
Understanding the functions parameter in the Chat Completions API.
Extracting structured JSON arguments from unstructured user prompts.
The 3-Step Request Chain (The industry standard for AI agents).
Implementing the function role in API messages.
Handling multiple parameters (Location, Units, etc.).
📍 Timestamps:
[00:03] - What is Function Calling in GPT-4?
[01:09] - Real-world Example: The Weather App Logic
[03:00] - Visualizing the Chain of Requests
[04:05] - Formatting Functions in JSON
[08:35] - Request #1: Sending Message + Function Definition
[11:05] - How the Model Extracts Function Arguments
[13:34] - Debugging: Why Content is "null" during a Function Call
[16:44] - Request #2: Calling the External Weather API (Axios)
[22:08] - Processing Weather Data (Celsius vs. Fahrenheit)
[35:26] - Request #3: Returning Data to GPT-4 for Natural Language
[39:25] - Understanding the NEW 'function' Role in API Messages
[41:40] - Final Demo: Weather in Multiple Languages
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