> ## Documentation Index
> Fetch the complete documentation index at: https://docs.squarecloud.app/llms.txt
> Use this file to discover all available pages before exploring further.

# How to Use Gunicorn

> Learn how to use Gunicorn, a Python HTTP server.

## Introduction

* This article guides you through the process of using Gunicorn, a Python WSGI HTTP server.
* Before we get started, make sure you have Python and Gunicorn installed in your environment. You can install Gunicorn using the following command:

```bash theme={null}
pip install gunicorn
```

## Basic usage

To run a Python web application using Gunicorn, you need to have a application WSGI like flask, django or some other framework.\
Once you have your application ready, you need to know the module name and the variable name that contains the WSGI application object.\
For example, if you have a Flask application in a file named `app.py` and the Flask instance is named `app`, you can run it with Gunicorn using the following command:

```bash theme={null}
python -m gunicorn --bind 0.0.0.0:80 app:app 
```

In this command:

* `python -m gunicorn` runs Gunicorn as a python module.
* `--bind 0.0.0.0:80` tells Gunicorn to listen on all network interfaces on port 80.
* `app:app` specifies the module name (`app`) and the variable name (`app`) that contains the WSGI application object.

## Additional options

Gunicorn provides several options to customize its behavior. Here we will show some options.

### Workers

* `--workers <number>`

This options sets the number of worker processes for handling requests. Generally use 2-4 workers per CPU core.\
You can calculate the number of workers using the formula: `(2 x $num_cores) + 1`.

### Name

* `--name <name>`
* `-n <name>`

This option sets the process name for Gunicorn.

### Worker-class

* `--worker-class <class>`
* `-k <class>`

This option sets the type of worker to use. The default is `sync`, but you can also use `gevent`, `eventlet`, `tornado` or other worker type.

### Paste

* `--paste <configfile>`

This option allows you to load a PasteDeploy configuration file.
This is useful for frameworks like Pyramid and Turbogear who use PasteDeploy files.

## Extras

Gunicorn has many more options and features that you can explore in the [official documentation](https://docs.gunicorn.org/en/stable/settings.html).

### Config file

* You can also create a configuration file to set Gunicorn options.
  This file can be in Python format and named `gunicorn.config.py`.

```python gunicorn.config.py theme={null}
import multiprocessing

bind = "0.0.0.0:80"
workers = multiprocessing.cpu_count() * 2 + 1
```

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