NitroUI

Build HTML with Python, not strings.

NitroUI is a zero-dependency Python library that lets you construct HTML documents using a clean, composable class-based API. No template files, no string concatenation, no runtime dependencies.

from nitro_ui import *

page = HTML(
    Head(Title("Dashboard")),
    Body(
        Nav(
            Link("Home", href="/"),
            Link("Settings", href="/settings", cls="active")
        ),
        Main(
            H1("Welcome back!"),
            Div(
                Paragraph("You have ", Strong("3"), " new notifications."),
                Button("View All", type="button", cls="btn-primary")
            )
        )
    )
)

print(page.render(pretty=True))

Why NitroUI?

• Type-safe: IDE autocomplete and type hints for every element
• Composable: Build reusable components as Python classes
• Zero dependencies: Just Python 3.8+, nothing else
• Framework agnostic: Works with FastAPI, Django, Flask, or standalone
• Serializable: Convert to/from JSON for drag-and-drop builders
• LLM-friendly: Perfect for AI-generated interfaces

Installation

pip install nitro-ui

Claude Code Skill

Add NitroUI as a skill in Claude Code for AI-assisted HTML generation:

npx skills add nitrosh/nitro-ui

Quick Examples

HTML-like Syntax

Prefer lowercase tag names that look like real HTML? Use nitro_ui.html:

from nitro_ui.html import div, h1, p, ul, li, a, img

page = div(
    h1("Welcome"),
    p("This looks just like HTML!"),
    ul(
        li(a("Home", href="/")),
        li(a("About", href="/about")),
    ),
    img(src="hero.jpg", alt="Hero image"),
    cls="container"
)

All standard HTML tags are available as lowercase functions. Python keywords use a trailing underscore: del_, input_, object_, map_.

Dynamic Content

from nitro_ui import *

def render_user_card(user):
    return Div(
        Image(src=user["avatar"], alt=user["name"]),
        H3(user["name"]),
        Paragraph(user["bio"]),
        Link("View Profile", href=f"/users/{user['id']}"),
        cls="user-card"
    )

users = [
    {"id": 1, "name": "Alice", "bio": "Backend engineer", "avatar": "/avatars/alice.jpg"},
    {"id": 2, "name": "Bob", "bio": "Frontend developer", "avatar": "/avatars/bob.jpg"},
]

grid = Div(*[render_user_card(u) for u in users], cls="user-grid")

Method Chaining

from nitro_ui import *

card = (Div()
    .add_attribute("id", "hero")
    .add_styles({"background": "linear-gradient(135deg, #667eea 0%, #764ba2 100%)", "padding": "4rem"})
    .append(H1("Ship faster with NitroUI"))
    .append(Paragraph("Stop fighting with templates. Start building.")))

Reusable Components

from nitro_ui import *

class Card(HTMLElement):
    def __init__(self, title, *children, **kwargs):
        super().__init__(**{**kwargs, "tag": "div"})
        self.add_attribute("class", "card")
        self.append(H3(title, cls="card-title"))
        for child in children:
            self.append(child)

class Alert(HTMLElement):
    def __init__(self, message, variant="info", **kwargs):
        super().__init__(**{**kwargs, "tag": "div"})
        self.add_attributes([("class", f"alert alert-{variant}"), ("role", "alert")])
        self.append(Paragraph(message))

# Usage
page = Div(
    Alert("Your changes have been saved.", variant="success"),
    Card("Statistics",
        Paragraph("Total users: 1,234"),
        Paragraph("Active today: 89")
    )
)

External Stylesheets with Themes

from nitro_ui import *
from nitro_ui.styles import CSSStyle, StyleSheet, Theme

# Use a preset theme
theme = Theme.modern()
stylesheet = StyleSheet(theme=theme)

# Register component styles
btn = stylesheet.register("btn", CSSStyle(
    background_color="var(--color-primary)",
    color="var(--color-white)",
    padding="var(--spacing-sm) var(--spacing-md)",
    border_radius="6px",
    border="none",
    cursor="pointer",
    _hover=CSSStyle(background_color="var(--color-primary-dark)")
))

# Use in your HTML
page = HTML(
    Head(
        Title("Styled Page"),
        Style(stylesheet.render())
    ),
    Body(
        Button("Click Me", cls=btn)
    )
)

Framework Integration

FastAPI

from fastapi import FastAPI
from fastapi.responses import HTMLResponse
from nitro_ui import *

app = FastAPI()

@app.get("/", response_class=HTMLResponse)
async def home():
    return HTML(
        Head(Title("FastAPI + NitroUI")),
        Body(H1("Hello from FastAPI"))
    ).render()

Flask

from flask import Flask
from nitro_ui import *

app = Flask(__name__)

@app.route("/")
def home():
    return HTML(
        Head(Title("Flask + NitroUI")),
        Body(H1("Hello from Flask"))
    ).render()

Django

from django.http import HttpResponse
from nitro_ui import *

def home(request):
    return HttpResponse(HTML(
        Head(Title("Django + NitroUI")),
        Body(H1("Hello from Django"))
    ).render())

Core Features

Pretty Printing

# Compact output (default) - ideal for production
page.render()

# Indented output - ideal for debugging
page.render(pretty=True)

JSON Serialization

Perfect for drag-and-drop builders, undo/redo, or API communication:

from nitro_ui import *
from nitro_ui.core.element import HTMLElement

# Serialize
json_data = page.to_json(indent=2)

# Deserialize
restored = HTMLElement.from_json(json_data)

HTML Parsing

Import existing HTML into NitroUI for manipulation:

from nitro_ui import from_html

element = from_html('<div class="card"><h1>Hello</h1></div>')
element.append(Paragraph("Added with NitroUI"))

Fragments

Group elements without a wrapper tag:

from nitro_ui import *

def table_rows(items):
    return Fragment(*[
        TableRow(TableDataCell(item["name"]), TableDataCell(item["price"]))
        for item in items
    ])

Raw HTML Partials

Embed raw HTML for trusted content like analytics tags:

from nitro_ui import Head, Meta, Title, Partial

Head(
    Meta(charset="utf-8"),
    Partial("""
        <!-- Google Analytics -->
        <script async src="https://www.googletagmanager.com/gtag/js?id=GA_ID"></script>
        <script>
            window.dataLayer = window.dataLayer || [];
            function gtag(){dataLayer.push(arguments);}
            gtag('js', new Date());
            gtag('config', 'GA_ID');
        </script>
    """),
    Title("My Page")
)

# Or load from a file (lazy-loaded at render time)
Partial(file="partials/analytics.html")

Warning: Partial bypasses HTML escaping. Only use with trusted content.

CSS Style Helpers

div = Div("Content")
div.add_style("color", "blue")
div.add_styles({"padding": "20px", "margin": "10px"})
div.remove_style("margin")
color = div.get_style("color")  # "blue"

Available Elements

PascalCase imports (from nitro_ui import *):

Module	Elements
nitro_ui.tags.html	HTML, Head, Body, Title, Meta, Script, Style, HtmlLink, IFrame
nitro_ui.tags.layout	Div, Section, Article, Header, Nav, Footer, Main, Aside, Dialog
nitro_ui.tags.text	H1-H6, Paragraph, Span, Strong, Em, Link, Code, Pre, Blockquote
nitro_ui.tags.form	Form, Input, Button, Select, Option, Textarea, Label, Fieldset
nitro_ui.tags.lists	UnorderedList, OrderedList, ListItem, DescriptionList
nitro_ui.tags.media	Image, Video, Audio, Figure, Canvas, Picture, Source
nitro_ui.tags.table	Table, TableRow, TableHeader, TableBody, TableHeaderCell, TableDataCell

Lowercase HTML-like imports (from nitro_ui.html import *):

Category	Aliases
Document	html, head, body, title, meta, script, style, link
Layout	div, section, article, header, nav, footer, main, hr
Text	h1-h6, p, span, strong, em, a, code, pre, b, i
Form	form, input_, button, select, option, textarea, label
Lists	ul, ol, li, dl, dt, dd
Media	img, video, audio, figure, canvas, picture, source
Table	table, tr, td, th, thead, tbody, tfoot

Note: input_, del_, object_, map_ use trailing underscore to avoid Python keyword/builtin conflicts.

Element API

Manipulation

• append(*children) / prepend(*children) - Add children
• clear() - Remove all children
• clone() - Deep copy element
• find_by_attribute(attr, value) - Find child by attribute

Attributes

• add_attribute(key, value) / add_attributes(list)
• get_attribute(key) / has_attribute(key)
• remove_attribute(key)

Styles

• add_style(prop, value) / add_styles(dict)
• get_style(prop) / remove_style(prop)

Output

• render(pretty=False) - Generate HTML string
• to_json() / from_json() - JSON serialization
• to_dict() / from_dict() - Dictionary conversion

All manipulation methods return self for chaining.

For AI/LLM Integration

NitroUI is designed to work seamlessly with AI code generation. See LLM_GUIDE.md for a complete technical reference including exact method signatures, type hints, and common patterns.

Development

# Setup
python3 -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"

# Run tests
pytest

# Format
black src/ tests/

License

BSD 3-Clause License. See LICENSE for details.

Links

• Author
• PyPI
• GitHub
• LLM Guide