Eel Python Library

Install the core Eel library using pip:

pip install eel

If you require support for HTML templating via Jinja2, install the optional dependency:

pip install eel[jinja2]

Eel is built on Gevent. To avoid blocking the event loop, avoid using time.sleep(). Instead, use eel.sleep() for non-blocking delays. To run a function in a separate greenlet (thread), use eel.spawn().

import eel
eel.init('web')

def my_other_thread():
    while True:
        print("I'm a thread")
        eel.sleep(1.0) # Use eel.sleep(), not time.sleep()

eel.spawn(my_other_thread)

eel.start('main.html', block=False)

while True:
    print("I'm a main loop")
    eel.sleep(1.0)

To package your Eel application into a standalone program that runs without a Python interpreter, use PyInstaller via the eel module.

1. Set up a virtual environment with your required Python version and packages.
2. Install PyInstaller: pip install PyInstaller.
3. Run the eel command to trigger the build process: python -m eel [your_main_script] [your_web_folder].
4. The build output will be located in a dist/ folder.

You can pass standard PyInstaller flags through the command. For example, use --exclude to omit specific modules or --onefile --noconsole to create a single executable windowed application.

To start an Eel application, first initialize the web files directory using eel.init() and then call eel.start() with the name of your entry HTML file. By default, this starts a webserver on http://localhost:8000 and opens the browser in App Mode if Chrome or Chromium is installed.

import eel
eel.init('web')
eel.start('main.html')

Eel uses tox to run tests against supported Python versions (3.7+).

Prerequisites:

• Chrome must be installed.
• A compatible ChromeDriver must be installed (ensure the ChromeDriver version matches your installed Chrome version).

Commands:

• To run tests against all supported versions: tox
• To run tests against a specific version (e.g., Python 3.6): tox -e py36

To develop with Eel, clone the repository, set up a virtual environment, and install the necessary requirements for production, testing, and metadata.

# Clone the repository
git clone git@github.com:python-eel/Eel.git

# Create and activate a virtual environment
python3 -m venv venv
source venv/bin/activate

# Install requirements
pip3 install -r requirements.txt        # eel's 'prod' requirements
pip3 install -r requirements-test.txt   # pytest and selenium
pip3 install -r requirements-meta.txt   # tox 

To make a JavaScript function callable from the Python backend, use eel.expose(function_name). You can optionally provide a second argument to override the exposed name, which is useful for minified builds.

eel.expose(my_javascript_function);
function my_javascript_function(a, b, c, d) {
  if (a < b) {
    console.log(c * d);
  }
}

# Calling from Python
eel.my_javascript_function(1, 2, 3, 4)

// Overriding name for minification
eel.expose(someFunction, "my_javascript_function");

To make a Python function callable from the frontend, decorate it with @eel.expose. On the JavaScript side, these functions will be available on the global eel object.

Note: You must include the Eel library in your HTML files via <script type="text/javascript" src="/eel.js"></script>.

@eel.expose
def my_python_function(a, b):
    print(a, b, a + b)

// In your HTML/JS file
eel.my_python_function(1, 2);