Streamsync is fully state-driven and provides separation of concerns between user interface and business logic.

import streamsync as ss

def handle_increment(state):
    state["counter"] += 1

ss.init_state({
    "counter": 0
})

import streamsync as ss

def handle_increment(state):
    state["counter"] += 1

ss.init_state({
    "counter": 0
})

The user interface is a template, which is defined visually. The template contains reactive references to state, e.g. @{counter}, and references to event handlers, e.g. when Button is clicked, trigger handle_increment.

• Event handling adds minimal overhead to your Python code (~1-2ms).
• The script only runs once.
• Non-blocking by default. Events are handled asynchronously in a thread pool running in a dedicated process.

• Version control everything. Development is local, user interfaces are saved as JSON.
• Use your local code editor and get instant refreshes when you save your code. Alternatively, use the provided web-based editor.
• You edit the UI while your app is running. What you see really is what you get.

• Elements are highly customisable with no CSS required, allowing for shadows, button icons, background colours, etc.
• HTML elements with custom CSS may be included using the HTML Element component. They can serve as containers for built-in components.