FastAPI Installation and Environment Setup

FastAPI requires Python 3.8 or higher. This section covers how to install FastAPI and configure the development environment.

Check Python version

Before installing FastAPI, verify your Python version:

$ python --version
Python 3.11.0

# 或者
$ python3 --version
Python 3.11.0

If your Python version is lower than 3.8, upgrade Python first.

Create virtual environment

It is recommended to install FastAPI in a virtual environment to avoid conflicts with system Python packages:

# 创建虚拟环境
$ python -m venv venv

# 激活虚拟环境（macOS/Linux）
$ source venv/bin/activate

# 激活虚拟环境（Windows）
$ venv\Scripts\activate

Virtual environments are a best practice in Python development. Using a separate virtual environment for each project avoids dependency conflicts between projects.

Install FastAPI

Install FastAPI using pip:

$ pip install fastapi

This command installs only the FastAPI core package. If you need to install FastAPI and all its optional dependencies at once, you can use:

$ pip install "fastapi[all]"

fastapi[all]The following components will be installed:

Package namePurpose
uvicorn[standard]ASGI server, used to run FastAPI applications
python-multipartForm data and file upload support
jinja2HTML template engine
python-jose[cryptography]JWT token support
passlib[bcrypt]Password hashing and encryption
python-dotenvEnvironment variable management

Install Uvicorn

FastAPI is an ASGI framework that requires an ASGI server to run. The most commonly used one is Uvicorn:

$ pip install "uvicorn[standard]"

[standard]This will install uvloop (a high-performance event loop) and httptools (a high-performance HTTP parser), significantly improving performance.

ASGI (Asynchronous Server Gateway Interface) is the standard interface between Python asynchronous web servers and applications, and is the asynchronous version of WSGI. Traditional frameworks such as Flask use WSGI (synchronous), while FastAPI uses ASGI (asynchronous), enabling more efficient handling of concurrent requests.

Run your first FastAPI application

After installation, create a file namedmain.pyFile:

Example

from fastapi import FastAPI

# Create FastAPI application instance
app = FastAPI()

# Define the GET route for the root path
@app.get("/")
async def root():
    return {"message": "Hello World"}

Start the application in the command line:

$ uvicorn main:app --reload

Parameter description:

ParameterDescription
main:appmainRefers to the file name main.py,appRefers to the FastAPI instance variable name created in the file
--reloadDevelopment mode: automatically reloads the server after code changes (for development environment only)

After successful startup, the terminal will display:

INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process
INFO:     Started server process
INFO:     Waiting for application startup.
INFO:     Application startup complete.

Open browser to accesshttp://127.0.0.1:8000, you will see the following JSON response:

{"message": "Hello World"}

Meanwhile, FastAPI automatically generates interactive API documentation:

AddressDocument typeDescription
http://127.0.0.1:8000/docsSwagger UIA documentation interface for interactively testing the API
http://127.0.0.1:8000/redocReDocA documentation interface that focuses more on reading experience

Using FastAPI CLI

The new version of FastAPI providesfastapiA command-line tool that makes it more convenient to run applications:

# 开发模式（自动重载）
$ fastapi dev

# 生产模式
$ fastapi run

fastapi devIt will automatically find FastAPI applications in the project and start the development server, equivalent touvicorn main:app --reload。

Recommended development tools

ToolsDescription
VS CodeFree and lightweight, offering an excellent FastAPI development experience with the Python and Pylance extensions
PyCharmA professional Python IDE with built-in FastAPI project templates and powerful debugging features
Alibaba QoderAn AI programming IDE launched by Alibaba, deeply customized based on VS Code
ByteDance TraeAn AI-driven development tool launched by ByteDance, with built-in Python support
It is recommended to use VS Code + Python extension, which has the best support for FastAPI type annotations and auto-completion, and is completely free.
other extensions