Slint Python API

Slint ↗ is a UI toolkit that supports different programming languages. Slint-python is the integration with Python.

This documentation describes slint 1.17.0b1.

Beta

Slint-python is in a beta phase of development: the APIs, while mostly stable, may be subject to further changes. Any changes are documented in the ChangeLog ↗. You can track the progress of the Python integration via the python-labelled issues ↗.

Prerequisites

• Python 3 ↗
• uv ↗ or pip ↗

Installation

Install Slint with uv or pip from the Python Package Index ↗:

uv add slint

bash

The installation uses binaries provided for macOS, Windows, and Linux for various architectures. If your target platform is not covered by binaries, uv will automatically build Slint from source. If that happens, you will need some software development tools on your machine, as well as Rust ↗.

Quick start

1. Create a new project with uv init.
2. Add the Slint Python package to your project: uv add slint.
3. Create a file called app-window.slint:

import { Button, VerticalBox } from "std-widgets.slint";

export component AppWindow inherits Window {
    in-out property<int> counter: 42;
    callback request-increase-value();
    VerticalBox {
        Text {
            text: "Counter: \{root.counter}";
        }
        Button {
            text: "Increase value";
            clicked => {
                root.request-increase-value();
            }
        }
    }
}

slint

4. Create a file called main.py:

import slint

# slint.loader will look in `sys.path` for `app-window.slint`.
class App(slint.loader.app_window.AppWindow):
    @slint.callback
    def request_increase_value(self):
        self.counter = self.counter + 1

app = App()
app.run()

python

5. Run it with uv run main.py.

Instantiating a component

Exported components are exposed as Python classes. To access such a class, you have two options:

1. Call load_file. The returned object is a namespace ↗ that provides every exported component that inherits Window:

   import slint
   components = slint.load_file("app.slint")
   main_window = components.MainWindow()

   python

2. Use Slint’s auto-loader, which lazily loads .slint files from sys.path:

   import slint
   main_window = slint.loader.app.MainWindow()

   python

Callbacks

Callbacks declared in .slint files are visible as callable properties on the component instance. Assign a Python callable to set a handler, or use the callback decorator when sub-classing:

import slint

class Component(slint.loader.my_component.MyComponent):
    @slint.callback
    def clicked(self):
        print("hello")

component = Component()

python

Arrays and models

Set array properties from Python by passing subclasses of Model. Use ListModel to construct a model from an iterable:

component.model = slint.ListModel([1, 2, 3])
component.model.append(4)
del component.model[0]

python

Type mappings

Each type used for properties in the Slint language translates to a specific Python type:

.slint type	Python type
int	int
float	float
string	str
color	Color
brush	Brush
image	Image
styled-text	StyledText
data-transfer	DataTransfer
length, physical-length, duration, angle	float
structure	dict / Struct
array	Model

For the full set of classes and module-level functions, see the API section in the sidebar.