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Fundamentals

5 topics

Before writing your first endpoint, learn the essentials — what APIs are, how to set up Python, manage environment variables, and structure your project.

Tip

FastAPI is built on standard Python and HTTP. Understanding these fundamentals will make every other concept click instantly.

Learning Progression

Step 1: What is an API?

Understand HTTP, JSON, and the request/response cycle that powers every web API.

What is an API?
HTTP, JSON, request/response — the foundation of every web API.
Python Setup
Virtual environments, pip, and requirements.txt — your development toolkit.
Environment Variables
.env files, python-dotenv, and pydantic-settings for secure configuration.
Project Structure
Organize routers, schemas, models, and config as your app grows.
Auto-Generated Docs
FastAPI’s /docs and /redoc — automatic interactive API documentation.

Explore: HTTP Methods

These are the patterns that trip up developers most often. Switch between Wrong and Fixed to compare the code side by side.

1
Not using a virtual environment
Installing packages globally leads to version conflicts
Don't do this
terminal
pip install fastapi
pip install uvicorn
# Installed globally — conflicts with other projects!
Always create a virtual environment for each project. This isolates dependencies and prevents version conflicts between projects.