Citry - Refreshingly simple UI

Citry is a frontend framework for Python. One component can own its HTML, browser behavior, CSS, translations, and Python event handlers, so you can build an interactive interface without maintaining a separate frontend application.

It feels familiar if you know HTML and Vue or React, and it works with FastAPI, Django, Flask, Starlette, ASGI, and WSGI applications.

Citry 0.4 is the public beta. It supports Python 3.10 through 3.14.

Read the docs · Try the playground · Explore examples · Install the VS Code extension · Browse Citry UI

Start with one component

Install Citry:

python -m pip install citry

Or add it to a uv project:

uv add citry

Define a component in ordinary Python. Typed inputs catch misspellings and missing values, while template_data() chooses exactly what the template can read:

from citry import Component


class Welcome(Component):
    class Kwargs:
        name: str
        messages: list[str]

    def template_data(self, kwargs, slots):
        return {
            "name": kwargs.name,
            "messages": kwargs.messages,
        }

    def css_data(self, kwargs, slots):
        return {"accent": "tomato"}

    template = """
      <section class="welcome">
        <h1>Welcome back, {{ name }}!</h1>
        <ul>
          <li c-for="message in messages">
            {{ message }}
          </li>
          <li c-empty>Nothing new yet.</li>
        </ul>
      </section>
    """

    css = """
      .welcome {
        border-top: 3px solid var(--accent);
      }
    """


html = str(
    Welcome(
        name="Ada",
        messages=["Build finished", "Report ready"],
    )
)

Components compose through HTML-like tags. Static inputs look like ordinary HTML attributes; prefix an input with c- when its value is a Python expression:

<main>
  <c-Welcome name="Ada" c-messages="user.inbox" />
</main>

That is most of the template language:

1. <c-Name> renders a component or a built-in control-flow tag.
2. A c- attribute evaluates a Python expression.

Continue with the step-by-step tutorial or read the template syntax guide.

Build the whole interface in Python

Citry gives each part of an interface a clear home:

Learn these features through the component guides, Events documentation, and advanced guides.

Need ready-made application components? Install Citry UI for accessible forms, dialogs, navigation, feedback, data display, theming, and translated default labels:

python -m pip install citry-ui

Connect a web application

Mount Citry on the web framework that already serves your application. For example, with FastAPI or Starlette:

from citry import citry
from citry.contrib.fastapi import mount


mount(app, citry)
citry.initialize()

Citry includes adapters for:

The web-framework guide shows the right startup and routing setup for each host.

Use the editor and command line

The free Citry extension for VS Code understands the HTML, Python, JavaScript, CSS, and Fluent inside a component. It provides completion, hover help, navigation, references, diagnostics, and safe formatting. The same extension is available from Open VSX.

Citry also installs a command-line checker:

citry check --static

Point it at an application for registered component contracts and template data:

citry --app myproject.app:citry_app check

See the VS Code guide and CLI reference for setup and CI usage.

Performance

The current benchmark renders a large page with about 350 Citry component markers and 986 KB of output, including browser runtimes and the component ownership graph:

• Compared with django-components, Citry is about 12% slower on the first render and 24% faster once warm.
• Compared with a bare Django template, Citry's warm render takes about 3.5 times as long while also running its component lifecycle, extension, dependency, ownership, and security work.
• Jinja2 remains the fastest no-component baseline once warm.

These are relative results from one machine. Read the published benchmark for the chart and interpretation, or the benchmark repository guide to reproduce it.

Get help and contribute

• Documentation
• Examples
• API reference
• Release notes
• Discord
• GitHub Discussions
• Issue tracker
• Contributing guide
• Sponsor Citry

Citry continues the component work begun in django-components and django-components/djc-core.

License

MIT