An Introduction to APIs: Understanding Inter-Program Communication from ScratchAn Introduction to APIs: Understanding Inter-Program Communication from Scratch

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0. Three Common Confusions for Beginners0. Three Common Confusions for Beginners

Confusion 1: Are APIs something advanced?Confusion 1: Are APIs something advanced?

Many people think APIs are only for senior engineers. But you've already used APIs:Many people think APIs are only for senior engineers. But you've already used APIs:

len("hello") # This is a Python API open("file.txt") # This is also an API requests.get(url) # This is still an API

Confusion 2: What's the difference between Web APIs and regular APIs?Confusion 2: What's the difference between Web APIs and regular APIs?

Confusion 3: Should I use HTTP or SDK?Confusion 3: Should I use HTTP or SDK?

# HTTP approach: handle all details yourself import requests response = requests.post( "https://api.deepseek.com/v1/chat/completions", headers={"Authorization": "Bearer sk-xxx"}, json={"model": "deepseek-chat", "messages": [...]} ) result = response.json()["choices"][0]["message"]["content"] # SDK approach: let the butler handle it from openai import OpenAI client = OpenAI(api_key="sk-xxx") response = client.chat.completions.create( model="deepseek-chat", messages=[...] ) result = response.choices[0].message.content

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1. The Essence of APIs: Plugs and Sockets1. The Essence of APIs: Plugs and Sockets

API (Application Programming Interface) is simply the "agreement for communication between programs."API (Application Programming Interface) is simply the "agreement for communication between programs."

1.1 Appliance Analogy1.1 Appliance Analogy

1.2 Three Types of API Comparison1.2 Three Types of API Comparison

1.3 Function API vs HTTP API: What's the Difference1.3 Function API vs HTTP API: What's the Difference

Many beginners wonder: what's the real difference between function APIs and HTTP APIs? How to tell them apart when reading documentation?Many beginners wonder: what's the real difference between function APIs and HTTP APIs? How to tell them apart when reading documentation?

1.4 How to Read Different Types of API Documentation1.4 How to Read Different Types of API Documentation

Different types of API documentation have different focus areas:Different types of API documentation have different focus areas:

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2. A Complete API Call2. A Complete API Call

👇 Try it out: Click the button below to observe a complete API request-response flow:👇 Try it out: Click the button below to observe a complete API request-response flow:

2.1 Four Stages of an API Call2.1 Four Stages of an API Call

2.2 Restaurant Analogy2.2 Restaurant Analogy

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3. HTTP Methods: Overview of You "Asking" or "Doing"3. HTTP Methods: Overview of You "Asking" or "Doing"

When calling a Web API, you need to tell the server what you want to do. That's where HTTP methods come in.When calling a Web API, you need to tell the server what you want to do. That's where HTTP methods come in.

3.1 Restaurant Ordering Analogy3.1 Restaurant Ordering Analogy

3.2 HTTP Methods Quick Reference3.2 HTTP Methods Quick Reference

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4. HTTP Status Codes: Overview of the Server Telling You4. HTTP Status Codes: Overview of the Server Telling You

When the server responds, it first returns a status code telling you whether the request was successful.When the server responds, it first returns a status code telling you whether the request was successful.

4.1 Status Code Categories4.1 Status Code Categories

4.2 Common Status Codes Explained4.2 Common Status Codes Explained

👇 Try it out: Click the button below to learn about common status codes:👇 Try it out: Click the button below to learn about common status codes:

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5. HTTP vs SDK: Run Errands Yourself or Let the Butler Handle It5. HTTP vs SDK: Run Errands Yourself or Let the Butler Handle It

5.1 Two Calling Methods Compared5.1 Two Calling Methods Compared

5.2 Approach to choosing5.2 Approach to choosing

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6. Approach to reading API Documentation6. Approach to reading API Documentation

API documentation is like a combination of a manual and a menu. You don't need to read it cover to cover — just learn how to "look things up in a dictionary."API documentation is like a combination of a manual and a menu. You don't need to read it cover to cover — just learn how to "look things up in a dictionary."

6.1 Documentation Reading Checklist6.1 Documentation Reading Checklist

Open any API documentation (like OpenAI or DeepSeek), and you only need to find these things:Open any API documentation (like OpenAI or DeepSeek), and you only need to find these things:

6.2 Steps to Read Documentation6.2 Steps to Read Documentation

1. Find the Base URL - This is the prefix for all requestsFind the Base URL - This is the prefix for all requests
2. Understand the authentication method - Is the API Key in the Header or Query?Understand the authentication method - Is the API Key in the Header or Query?
3. Find the Endpoint you need - The specific endpoint you want to callFind the Endpoint you need - The specific endpoint you want to call
4. Check request parameters - Which are required? Which are optional?Check request parameters - Which are required? Which are optional?
5. Understand the response format - How is the data organized?Understand the response format - How is the data organized?

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7. Hands-on Practice: Simulate API Calls7. Hands-on Practice: Simulate API Calls

Practice makes perfect. Here's a simulated API where you can fill in any parameters and change any address to see what happens.Practice makes perfect. Here's a simulated API where you can fill in any parameters and change any address to see what happens.

Try triggering these scenarios:Try triggering these scenarios:

• ✅ Successful request: Enter the correct Endpoint and API Key✅ Successful request: Enter the correct Endpoint and API Key
• ❌ 401 Error: Don't enter an API Key and see how the server rejects you❌ 401 Error: Don't enter an API Key and see how the server rejects you
• ❌ 404 Error: Enter a non-existent address❌ 404 Error: Enter a non-existent address

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8. Summary8. Summary

📖 Konsep Penting📖 Core Concept

1. APIs are like megaphones, helping you pass messages to other code or remote servers 2. You've already used APIs, from len() to open(), they're all APIs 3. Web APIs are superpowers, letting you call supercomputers thousands of miles away 4. SDKs are good butlers, use SDKs when available instead of running errands yourself 5. Look for three things in documentation: address, authentication, and parameters1. APIs are like megaphones, helping you pass messages to other code or remote servers 2. You've already used APIs, from len() to open(), they're all APIs 3. Web APIs are superpowers, letting you call supercomputers thousands of miles away 4. SDKs are good butlers, use SDKs when available instead of running errands yourself 5. Look for three things in documentation: address, authentication, and parameters

In the era of AI programming, you only need to remember these core concepts. The rest of the details will be handled by your IDE and AI assistant.In the era of AI programming, you only need to remember these core concepts. The rest of the details will be handled by your IDE and AI assistant.

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GlossaryGlossary

Term	Full Name	Explanation
API	Application Programming Interface	Application programming interface, defines how software interacts
Web API	-	HTTP-based API for network communication
Endpoint	-	Endpoint, the specific address of an API
HTTP	HyperText Transfer Protocol	Communication protocol used by Web APIs
GET	-	Method for retrieving resources
POST	-	Method for submitting data
SDK	Software Development Kit	Software development kit that wraps underlying API calls
URL	Uniform Resource Locator	Network address of an API
JSON	JavaScript Object Notation	Commonly used data format
Authentication	-	Process of verifying identity
Status Code	-	Status code in HTTP responses
Request	-	Request
Response	-	Response
Header	-	HTTP header containing metadata
Payload	-	Actual data in a request or response
Rate Limit	-	Rate limiting
Idempotent	-	Idempotent, multiple executions produce the same result
REST	Representational State Transfer	An API architectural style
RPC	Remote Procedure Call	Remote procedure call
GraphQL	-	A query language API
gRPC	-	High-performance RPC framework developed by Google

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