ABC TO XYZ OF AI

Let’s go step-by-step So First ALL ABOUT API👇

🧩 1️⃣ What is an API?

API stands for Application Programming Interface.
It is a set of rules and endpoints that allows two applications or systems to communicate with each other.

Think of it as a messenger between two programs:

• You send a request → API delivers it to another system
• That system processes it → API brings back the response

💡 Example

• When your mobile app shows today’s weather — it calls a Weather API.
• When you log in using Google — the app calls Google’s Authentication API.
• When your Python code fetches stock prices — it calls a Finance API.

⚙️ 2️⃣ Use Cases of APIs

🌐 3️⃣ What is a RESTful API?

REST (Representational State Transfer) is a style or design pattern for building APIs.

A RESTful API is simply an API that follows REST principles.

Let’s break down Representational State Transfer (REST) — the full form of RESTful API — word by word to understand what each means and why it matters 👇

🧩 1️⃣ Representational

• Meaning: The way a resource (like a piece of data) is represented when it is transferred between client and server.
• Example:
  Suppose you request a user profile from a REST API.
  • The resource = the user profile
  • The representation could be in JSON, XML, HTML, or even plain text.
• So, the server sends a representation of the resource — not the resource itself.

🧠 Think: “I don’t send you the database row; I send you a representation (like JSON) of it.”

🔁 2️⃣ State

• Meaning: The state refers to the data or condition of the resource at a specific time.
• REST is stateless, meaning:
  • The server does not store any client context between requests.
  • Each request from the client must contain all necessary information (like authentication tokens, parameters, etc.) for the server to understand and respond.

📌 Example:

• If you log in and fetch your account details, every request you send must include your authentication token — the server doesn’t “remember” you.

🧠 Think: “Each request carries its own state information.”

🚚 3️⃣ Transfer

• Meaning: The movement or exchange of data between the client and server using standard HTTP methods.
• Common HTTP verbs (methods):
  • GET → Retrieve data
  • POST → Create data
  • PUT → Update/replace data
  • PATCH → Partially update data
  • DELETE → Remove data

🧠 Think: “Transfer the representation of a resource’s state over HTTP.”

🧠 Putting It All Together

🔄 Simple Analogy

Imagine you order pizza online 🍕

• The resource is the pizza itself.
• The representation is the image or order details (like JSON data).
• The state is the order status (ordered, baking, delivered).
• The transfer is when this info moves between your app (client) and the restaurant server (API).

🔸 Key REST Principles

💡 Example of a RESTful API

🆚 Difference between API and RESTful API

🐍 4️⃣ Python Modules for Creating APIs

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