How to Install Uvicorn: A Simple Setup Guide for Python Developers

Learn how to quickly and easily set up Uvicorn, a lightning-fast web server for your modern Python applications.

gunicorn

Getting Started with Modern Python Web Servers

UNIX

What Exactly is Uvicorn?

Uvicorn is a super-fast web server designed specifically for Python. When you build a web application or an API using modern Python frameworks like FastAPI or Starlette, you need a program to actually serve it to the internet. Uvicorn acts as the bridge between your Python code and the users who are trying to access your website from their web browsers.

What makes Uvicorn special is that it uses a modern standard called "ASGI" (Asynchronous Server Gateway Interface). In simple terms, this means Uvicorn can handle many different tasks at the exact same time without getting stuck waiting for one task to finish. Because of this, it is incredibly fast and can easily manage a huge number of users visiting your application all at once.

Before Uvicorn and ASGI existed, older Python web servers usually had to handle requests one by one in a line. Uvicorn changed the game by bringing the power of "asynchronous" (non-blocking) programming to Python web servers. Today, it is the standard and most popular choice for developers who want to run high-performance Python web applications easily.

Prerequisites

  • Internet Connection: An active connection to download the required packages.
  • Operating System: A computer running Windows, macOS, or Linux.
  • Python Installed: Python version 3.10 or newer installed on your system.
  • Command Line: Basic knowledge of how to open and use a command-line interface (Terminal on Mac/Linux, or Command Prompt/PowerShell on Windows).
  • Package Manager: pip (Python's default package installer) available on your computer.

Step-by-Step Installation

1

Verify Python Installation

First, open your terminal or command prompt and check that Python is installed and running a supported version (3.10+).
BASH 
python --version
2

Create and Activate a Virtual Environment

It is highly recommended to install Python packages inside a virtual environment to keep your project files organized and prevent conflicts with other projects.
Create the environment:
BASH 
python -m venv .venv
Activate the environment (macOS/Linux):
BASH 
source .venv/bin/activate
Activate the environment (Windows):
BASH 
.venv\Scripts\activate
3

Install Uvicorn

There are two ways to install Uvicorn. We recommend the "Standard" installation for the best speed and performance.
Option A: The Standard Installation (Recommended)
This installs Uvicorn along with extra tools that make it run much faster. This is the best choice for almost all developers.
BASH 
pip install 'uvicorn[standard]'
Option B: The Minimal Installation
If you want a very small footprint or are working on a system that cannot install extra C-based tools, you can install the pure Python version.
BASH 
pip install uvicorn
4

Verify the Installation

Check that Uvicorn was installed successfully by asking for its version number.
Bash 
uvicorn --version
5

Test the Server with a Basic App

To prove your new server works, create a simple Python file and run it.
1. Create a file named example.py and paste this code inside:
Python 
async def app(scope, receive, send):
    assert scope['type'] == 'http'
    
    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            (b'content-type', b'text/plain'),
            (b'content-length', b'13'),
        ],
    })
    
    await send({
        'type': 'http.response.body',
        'body': b'Hello, world!',
    })
2. Run the server from your terminal:
Bash 
uvicorn example:app --reload
Congratulations! You can now open your web browser and go to http://127.0.0.1:8000 to see your running Uvicorn server display "Hello, world!".

Final Thoughts

You have now successfully set up a high-performance foundation for your modern Python web applications.

  • Verified Python: You confirmed your system meets the required versions to run modern frameworks.
  • Created a Virtual Environment: You set up a safe, isolated workspace to keep your project files and packages organized.
  • Installed Uvicorn: You downloaded and installed the lightning-fast ASGI web server.
  • Tested the Server: You wrote a basic Python script and successfully launched it to the web browser.

With Uvicorn up and running, you are fully prepared to start building and deploying fast, scalable APIs and websites.

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