FastAPI Setting Up Development Environment

Before you write any FastAPI code, your computer needs the right tools installed. This topic walks you through every step from a blank machine to a running FastAPI server.

What You Need Before Starting

You need Python 3.8 or higher. FastAPI uses modern Python features that older versions do not support. Check your version by running this in your terminal:

python --version

If you see Python 3.8.x or higher, you are ready. If Python is not installed, download it from python.org and run the installer.

Create a Project Folder

Keep your code organized from the start. Create a dedicated folder for your FastAPI project:

mkdir my-fastapi-project
cd my-fastapi-project

Use a Virtual Environment

A virtual environment is like a private box for your project's packages. Libraries you install inside this box do not affect the rest of your computer, and libraries from other projects cannot interfere with yours.

Your Computer
│
├── Project A (virtual env)
│     └── fastapi 0.100, pydantic 2.x
│
└── Project B (virtual env)
      └── fastapi 0.88, pydantic 1.x

Create and activate the virtual environment:

On Windows

python -m venv venv
venv\Scripts\activate

On macOS or Linux

python -m venv venv
source venv/bin/activate

Your terminal prompt changes to show (venv) at the start. That confirms the virtual environment is active.

Install FastAPI and Uvicorn

You need two packages. FastAPI is the framework. Uvicorn is the server that actually runs your FastAPI app and listens for requests.

pip install fastapi uvicorn

Here is how they work together:

Browser / Client
      |
      | HTTP request
      v
  [ Uvicorn ]      ← the server (listens on port 8000)
      |
      | passes request to
      v
  [ FastAPI App ]  ← your Python code
      |
      | returns response
      v
  [ Uvicorn ]
      |
      v
Browser / Client

Verify Your Installation

Check that both packages installed correctly:

pip show fastapi
pip show uvicorn

You see version information for each package. No errors means the installation succeeded.

Choose a Code Editor

Any text editor works, but Visual Studio Code (free, from Microsoft) gives you the best experience for FastAPI development. Install the Python extension inside VS Code to get autocomplete, error highlighting, and debugging support.

Create Your First File

Create a file called main.py in your project folder and paste this code:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"status": "FastAPI is running!"}

Start the Server

Run this command in your terminal from inside the project folder:

uvicorn main:app --reload

The main part refers to your main.py file. The app part refers to the app = FastAPI() object inside it. The --reload flag tells Uvicorn to restart automatically every time you save a change to your code.

You see output like this:

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process

Open your browser and visit http://127.0.0.1:8000. You see {"status": "FastAPI is running!"}.

Explore the Automatic Docs

Visit http://127.0.0.1:8000/docs in your browser. FastAPI shows you an interactive documentation page — already built, without you writing anything extra.

Key Points

• Python 3.8 or higher is required.
• Always use a virtual environment to keep project dependencies separate.
• Install both fastapi and uvicorn with pip.
• Run your app with uvicorn main:app --reload.
• Your app is live at http://127.0.0.1:8000 and docs at /docs.