Chapter 1: Getting Started with Tina4 Python

1. What Is Tina4 Python

Tina4 Python is a zero-dependency web framework for Python 3.12+. One package. Routing, ORM, template engine, authentication, queues, WebSocket, and 70 other features -- all built in.

It belongs to the Tina4 family -- four identical frameworks in Python, PHP, Ruby, and Node.js. Everything you learn here transfers to the other three. Same project structure. Same template syntax. Same CLI commands. Same .env variables.

Tina4 Python follows Python convention: snake_case for methods and functions (fetch_one(), soft_delete(), has_many()), PascalCase for classes, UPPER_SNAKE_CASE for constants. Route handlers are async def functions decorated with @get, @post, and friends.

By the end of this chapter, you will have a running Tina4 Python project with an API endpoint and a rendered HTML page.

---

2. Prerequisites and Installation

What You Need

Three tools. Nothing else.

1. Python 3.12 or later -- check with:

python3 --version

You should see output like:

Python 3.12.3

If you see a version lower than 3.12, upgrade Python first.

2. uv -- a fast Python package manager and project tool. Check with:

uv --version

You should see:

uv 0.6.9

If uv is not installed, get it from https://docs.astral.sh/uv/:

# macOS / Linux
curl -LsSf https://astral.sh/uv/install.sh | sh

# Windows (PowerShell)
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

3. The Tina4 CLI -- a Rust-based binary that manages all four Tina4 frameworks:

macOS (Homebrew):

brew install tina4stack/tap/tina4

Linux / macOS (install script):

curl -fsSL https://raw.githubusercontent.com/tina4stack/tina4/main/install.sh | bash

Windows (PowerShell):

irm https://raw.githubusercontent.com/tina4stack/tina4/main/install.ps1 | iex

Verify the CLI is installed:

tina4 --version

tina4 0.1.0

Installing the Tina4 CLI

cargo install tina4

Or download from GitHub Releases.

The tina4 CLI manages project scaffolding, development servers, migrations, and more across all Tina4 frameworks.

Creating a New Project

One command. One package. No dependency tree.

tina4 init python my-store

tina4 init installs the Tina4 CLI globally (via cargo, homebrew, or direct download), then scaffolds a complete project with routes, templates, database, and configuration.

You should see:

Creating Tina4 project in ./my-store ...
  Detected language: Python (pyproject.toml)
  Created .env
  Created .env.example
  Created .gitignore
  Created src/routes/
  Created src/orm/
  Created src/migrations/
  Created src/seeds/
  Created src/templates/
  Created src/templates/errors/
  Created src/public/
  Created src/public/js/
  Created src/public/css/
  Created src/public/scss/
  Created src/public/images/
  Created src/public/icons/
  Created src/locales/
  Created data/
  Created logs/
  Created secrets/
  Created tests/

Project created! Next steps:
  cd my-store
  uv sync
  tina4 serve

Install the Python dependencies:

cd my-store
uv sync

Resolved 1 package in 0.8s
Installed 1 package in 0.3s
 + tina4-python==3.1.0

One package. No dependency tree. No version conflicts. Just tina4-python.

Starting the Dev Server

tina4 serve

 _____ _             _  _
|_   _(_)_ __   __ _| || |
  | | | | '_ \ / _` | || |_
  | | | | | | | (_| |__   _|
  |_| |_|_| |_|\__,_|  |_|

  Tina4 Python v3.2.0
  Server running at http://0.0.0.0:7145
  Debug mode: ON
  Database: sqlite:///data/app.db
  Press Ctrl+C to stop

Open your browser to http://localhost:7145. The Tina4 welcome page greets you.

Open http://localhost:7145/health in your browser or curl it:

curl http://localhost:7145/health

{
  "status": "ok",
  "database": "connected",
  "uptime_seconds": 12,
  "version": "3.2.0",
  "framework": "tina4-python"
}

Your Tina4 Python project is running.

---

3. Project Structure Walkthrough

Here is what tina4 init created:

my-store/
├── .env                    # Your configuration (gitignored)
├── .env.example            # Template for other developers
├── .gitignore              # Pre-configured
├── pyproject.toml          # Python project definition (uv / pip)
├── .venv/                  # Virtual environment (gitignored)
├── src/
│   ├── routes/             # Your route handlers go here
│   ├── orm/                # Your ORM model classes go here
│   ├── migrations/         # SQL migration files
│   ├── seeds/              # Database seed files
│   ├── templates/          # Frond templates
│   │   └── errors/         # Custom 404.html, 500.html
│   ├── public/             # Static files (CSS, JS, images)
│   │   ├── js/
│   │   │   └── frond.js    # Auto-provided JS helper library
│   │   ├── css/
│   │   │   └── tina4.css   # Built-in CSS utility framework
│   │   ├── scss/
│   │   ├── images/
│   │   └── icons/
│   └── locales/            # Translation files
│       └── en.json
├── data/                   # SQLite databases (gitignored)
├── logs/                   # Log files (gitignored)
├── secrets/                # JWT keys (gitignored)
└── tests/                  # Your test files

Key directories:

• src/routes/ -- Every .py file here is auto-loaded at startup. Drop your route definitions here. Organize into subdirectories if you want.
• src/orm/ -- Every .py file here is auto-loaded. Drop your ORM model classes here.
• src/templates/ -- Frond (Tina4's built-in template engine -- see Chapter 4: Templates) looks here when you call response.render("my-page.html", data).
• src/public/ -- Files served directly. src/public/images/logo.png lives at /images/logo.png.
• data/ -- The default SQLite database (app.db) lives here. Gitignored because databases do not belong in version control.

---

4. Your First Route

Create the file src/routes/greeting.py:

from tina4_python.core.router import get

@get("/api/greeting/{name}")
async def greeting(name, request, response):
    from datetime import datetime
    return response.json({
        "message": f"Hello, {name}!",
        "timestamp": datetime.now().isoformat()
    })

In Python, path parameters are passed directly as function arguments -- not via request.params. The parameter name in the function signature must match the {name} in the route pattern.

Save the file. The dev server picks up the change through live reload. If not, restart with tina4 serve.

Test It

Open your browser to:

http://localhost:7145/api/greeting/Alice

You should see:

{
  "message": "Hello, Alice!",
  "timestamp": "2026-03-22T14:30:00.000000"
}

Or use curl:

curl http://localhost:7145/api/greeting/Alice

{"message":"Hello, Alice!","timestamp":"2026-03-22T14:30:00.000000"}

The browser shows pretty-printed JSON (browser extensions or dev mode). Curl shows compact JSON. Force pretty output with ?pretty=true:

curl "http://localhost:7145/api/greeting/Alice?pretty=true"

{
  "message": "Hello, Alice!",
  "timestamp": "2026-03-22T14:30:00.000000"
}

Understanding What Happened

Five steps. No magic.

1. You created a file in src/routes/. Tina4 auto-discovered it at startup.
2. @get("/api/greeting/{name}") registered a GET route with a path parameter {name}.
3. When you requested /api/greeting/Alice, the router matched the pattern and called your handler.
4. The router extracted "Alice" from the URL and passed it as the name argument to your function.
5. response.json(...) serialized the dictionary to JSON, set Content-Type: application/json, and returned a 200 OK.

Adding More HTTP Methods

Update src/routes/greeting.py:

from tina4_python.core.router import get, post

@get("/api/greeting/{name}")
async def greeting(name, request, response):
    from datetime import datetime
    return response.json({
        "message": f"Hello, {name}!",
        "timestamp": datetime.now().isoformat()
    })

@post("/api/greeting")
async def create_greeting(request, response):
    name = request.body.get("name", "World")
    language = request.body.get("language", "en")

    greetings = {
        "en": "Hello",
        "es": "Hola",
        "fr": "Bonjour",
        "de": "Hallo",
        "ja": "Konnichiwa"
    }

    greeting_word = greetings.get(language, greetings["en"])

    return response.json({
        "message": f"{greeting_word}, {name}!",
        "language": language
    }, 201)

Test the POST endpoint:

curl -X POST http://localhost:7145/api/greeting \
  -H "Content-Type: application/json" \
  -d '{"name": "Carlos", "language": "es"}'

{"message":"Hola, Carlos!","language":"es"}

The HTTP status code is 201 Created (the second argument to response.json()).

---

5. Your First Template

Tina4 uses the Frond template engine -- a zero-dependency, Twig-compatible engine built from scratch. If you have used Twig, Jinja2, or Nunjucks, Frond will feel familiar.

Create a Base Layout

Create src/templates/base.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{% block title %}My Store{% endblock %}</title>
    <link rel="stylesheet" href="/css/tina4.css">
    <style>
        body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; margin: 0; padding: 0; }
        .container { max-width: 960px; margin: 0 auto; padding: 20px; }
        .product-card { border: 1px solid #ddd; border-radius: 8px; padding: 16px; margin: 8px 0; }
        .product-card h3 { margin-top: 0; }
        .price { color: #2d8f2d; font-weight: bold; font-size: 1.2em; }
        .badge { display: inline-block; padding: 2px 8px; border-radius: 4px; font-size: 0.8em; }
        .badge-success { background: #d4edda; color: #155724; }
        .badge-danger { background: #f8d7da; color: #721c24; }
        nav { background: #333; color: white; padding: 12px 20px; }
        nav a { color: white; text-decoration: none; margin-right: 16px; }
    </style>
</head>
<body>
    <nav>
        <a href="/">Home</a>
        <a href="/products">Products</a>
    </nav>
    <div class="container">
        {% block content %}{% endblock %}
    </div>
    <script src="/js/frond.js"></script>
</body>
</html>

This base layout defines two blocks (title and content) that child templates override. It includes tina4.css (the built-in CSS framework) and frond.js (the built-in JS helper library).

Create a Product Listing Page

Create src/templates/products.html:

{% extends "base.html" %}

{% block title %}Products - My Store{% endblock %}

{% block content %}
    <h1>Our Products</h1>
    <p>Showing {{ products | length }} product{{ "s" if products|length != 1 else "" }}</p>

    {% if products %}
        {% for product in products %}
            <div class="product-card">
                <h3>{{ product.name }}</h3>
                <p>{{ product.description }}</p>
                <p class="price">${{ "%.2f"|format(product.price) }}</p>
                {% if product.in_stock %}
                    <span class="badge badge-success">In Stock</span>
                {% else %}
                    <span class="badge badge-danger">Out of Stock</span>
                {% endif %}
            </div>
        {% endfor %}
    {% else %}
        <p>No products available at the moment.</p>
    {% endif %}
{% endblock %}

Create the Route That Renders the Template

Create src/routes/pages.py:

from tina4_python.core.router import get

@get("/products")
async def products_page(request, response):
    products = [
        {
            "name": "Wireless Keyboard",
            "description": "Ergonomic wireless keyboard with backlit keys.",
            "price": 79.99,
            "in_stock": True
        },
        {
            "name": "USB-C Hub",
            "description": "7-port USB-C hub with HDMI, SD card reader, and Ethernet.",
            "price": 49.99,
            "in_stock": True
        },
        {
            "name": "Monitor Stand",
            "description": "Adjustable aluminum monitor stand with cable management.",
            "price": 129.99,
            "in_stock": False
        },
        {
            "name": "Mechanical Mouse",
            "description": "High-precision wireless mouse with 16,000 DPI sensor.",
            "price": 59.99,
            "in_stock": True
        }
    ]

    return response.render("products.html", {"products": products})

See It in the Browser

Open http://localhost:7145/products. You should see:

• A dark navigation bar with "Home" and "Products" links
• The heading "Our Products"
• A subheading showing "Showing 4 products"
• Four product cards, each with name, description, price, and stock badge
• The "Monitor Stand" card shows a red "Out of Stock" badge
• The other three show green "In Stock" badges

How Template Rendering Works

Eight steps. All automatic.

1. response.render("products.html", {"products": products}) tells Frond to render src/templates/products.html with the given data.

2. Frond sees {% extends "base.html" %} and loads the base template.
3. The {% block content %} in products.html replaces the same block in base.html.
4. {{ product.name }} outputs the value, auto-escaped for HTML safety.
5. {{ "%.2f"|format(product.price) }} formats the number with 2 decimal places.
6. {% for product in products %} loops through the list.
7. {% if product.in_stock %} renders the stock badge conditionally.
8. {{ products | length }} returns the item count.

About tina4css

The tina4.css file is Tina4's built-in CSS utility framework. Layout utilities. Typography. Common UI patterns. No Bootstrap. No Tailwind. No download. It ships with every scaffolded project.

---

6. Understanding .env

Open the .env file at the root of your project:

TINA4_DEBUG=true

That is likely all you see. The scaffold creates a minimal .env with debug mode enabled. Everything else uses defaults.

The important defaults for development:

Variable	Default Value	What It Means
TINA4_PORT	7145	Default server port (override with tina4 serve --port)
DATABASE_URL	sqlite:///data/app.db	SQLite database in the data/ directory
TINA4_LOG_LEVEL	ALL	All log messages are output
CORS_ORIGINS	*	All origins allowed (fine for development)
TINA4_RATE_LIMIT	60	60 requests per minute per IP

Log levels control how much output Tina4 produces:

Level	Behaviour
ALL / DEBUG	Full verbose output. DevReload active (live-reload, error overlay, hot-patching).
INFO	Standard logging. Startup messages, request summaries.
WARNING	Warnings and errors only.
ERROR	Errors only. Minimal output.

Set TINA4_LOG_LEVEL=DEBUG during development for maximum visibility. Use WARNING or ERROR in production.

To change the port, use the CLI flag or .env:

tina4 serve --port 8080

Or add it to your .env file:

TINA4_DEBUG=true
TINA4_PORT=8080

Restart the server. It now runs on port 8080.

How port resolution works: The Rust CLI (tina4 serve) determines the port using this priority order:

1. CLI flag (highest priority): tina4 serve --port 8080
2. .env file: TINA4_PORT=8080
3. Environment variable: PORT=8080
4. Framework default (Python: 7145, PHP: 7146, Ruby: 7144, Node.js: 7143)

The CLI reads your .env file and checks for TINA4_PORT (and falls back to PORT). The resolved port is passed to the Python server. All three methods work -- use whichever fits your workflow.

For the complete .env reference with all 68 variables, see Book 0, Chapter 4: Environment Variables.

---

7. The Dev Dashboard

With TINA4_DEBUG=true in your .env, Tina4 provides a built-in development dashboard. No additional environment variables are needed.

Restart the server and navigate to:

http://localhost:7145/__dev

The dashboard shows:

• System Overview -- framework version, Python version, uptime, memory usage, database status
• Request Inspector -- recent HTTP requests with method, path, status, duration, and request ID. Click any request to see full headers, body, database queries, and template renders.
• Error Log -- unhandled exceptions with stack traces and occurrence counts
• Queue Manager -- queue status (pending, reserved, failed, dead-letter messages)
• WebSocket Monitor -- active WebSocket connections with metadata
• Routes -- all registered routes with their methods, paths, and middleware

The dev dashboard shows you what your application is doing without adding print statements or log calls.

When you visit any HTML page (like /products), a debug overlay appears -- a toolbar at the bottom showing:

• Request details (method, URL, duration)
• Database queries executed (with timing)
• Template renders (with timing)
• Session data
• Recent log entries

This overlay is only visible when TINA4_DEBUG=true. Production never sees it.

---

8. Manual Setup (No CLI)

The tina4 CLI scaffolds everything for you. But sometimes you create a project from scratch — an empty folder, a fresh virtual environment, no CLI installed yet. Here is the minimum you need.

Step 1: Install the Package

pip install tina4-python

Or with uv:

uv add tina4-python

Step 2: Create app.py

This is the entry point. Create a file called app.py in your project root:

"""Tina4 Application."""
from tina4_python.core import run

if __name__ == "__main__":
    run()

That is the entire file. The run() function starts the web server, scans for routes, and loads templates.

Step 3: Create the Folder Structure

Tina4 expects this layout:

my-project/
├── app.py
├── .env
└── src/
    ├── routes/       # Route files go here
    ├── templates/    # Twig templates go here
    └── public/       # Static files (CSS, JS, images)

Create the directories:

mkdir -p src/routes src/templates src/public

Step 4: Create .env

TINA4_DEBUG=true

Step 5: Run It

python app.py

The server starts on http://localhost:7145. You should see the Tina4 welcome page. From here, add route files in src/routes/ and templates in src/templates/ — the same way as a CLI-scaffolded project.

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9. Request & Response Fundamentals

Before jumping into the exercises, let's consolidate how route handlers work in Tina4 Python. Every handler receives two objects: request (what the client sent) and response (what you send back). Here is the complete picture.

Reading Query Parameters

Query parameters are the key-value pairs after the ? in a URL. Access them through request.params:

# URL: /api/search?q=laptop&page=2
request.params.get("q", "")       # "laptop"
request.params.get("page", "1")   # "2" (always a string)
request.params.get("sort", "name") # "name" (default -- param was not sent)

Reading URL Path Parameters

Route patterns like /users/{id} capture segments of the URL. In Tina4 Python, path parameters arrive as function arguments:

from tina4_python.core.router import get

@get("/users/{id:int}/posts/{slug}")
async def user_post(id, slug, request, response):
    # id = 5 (int, because of :int type hint)
    # slug = "hello-world" (string)
    return response.json({"user_id": id, "slug": slug})

The {id:int} syntax tells Tina4 to convert the value to an integer. Without :int, it stays a string.

Reading the Request Body

POST, PUT, and PATCH requests carry a body. Tina4 parses JSON bodies into a dictionary automatically (as long as the client sends Content-Type: application/json):

from tina4_python.core.router import post

@post("/api/items")
async def create_item(request, response):
    name = request.body.get("name", "")
    price = request.body.get("price", 0)
    return response.json({"received_name": name, "received_price": price})

Reading Headers

Headers are available as a dictionary. Header names are case-insensitive:

content_type = request.headers.get("Content-Type", "not set")
auth_token = request.headers.get("Authorization", "")
custom = request.headers.get("X-Custom-Header", "")

Sending JSON Responses

response.json() converts a dictionary to JSON and sets the correct Content-Type. Pass a status code as the second argument:

return response.json({"id": 1, "name": "Widget"})        # 200 OK (default)
return response.json({"id": 1, "name": "Widget"}, 201)    # 201 Created
return response.json({"error": "Not found"}, 404)          # 404 Not Found

Sending HTML / Template Responses

response.render() renders a Frond template from src/templates/ and passes data to it:

return response.render("products.html", {"products": product_list, "title": "Our Products"})

For raw HTML without a template file:

return response.html("<h1>Hello</h1><p>This works too.</p>")

Status Codes

The most common status codes you will use:

Code	Meaning	When to Use
200	OK	Successful GET (default)
201	Created	Successful POST that created something
400	Bad Request	Client sent invalid input
404	Not Found	Resource does not exist
500	Internal Server Error	Something broke on the server

Worked Example: A Complete Route File

Here is a full route file that ties everything together. It builds a small book lookup API with query parameters, path parameters, JSON responses, and proper status codes. Read through it before attempting the exercises -- it is your reference.

Create src/routes/books.py:

from tina4_python.core.router import get, post

# In-memory data store
books = [
    {"id": 1, "title": "Dune", "author": "Frank Herbert", "year": 1965},
    {"id": 2, "title": "Neuromancer", "author": "William Gibson", "year": 1984},
    {"id": 3, "title": "Snow Crash", "author": "Neal Stephenson", "year": 1992}
]


@get("/api/books")
async def list_books(request, response):
    """List all books. Supports ?author= filter and ?sort=year."""
    author = request.params.get("author", "")
    sort_by = request.params.get("sort", "")

    result = books

    # Filter by author if the query param is present
    if author:
        result = [b for b in result if author.lower() in b["author"].lower()]

    # Sort by year if requested
    if sort_by == "year":
        result = sorted(result, key=lambda b: b["year"])

    return response.json({"books": result, "count": len(result)})


@get("/api/books/{id:int}")
async def get_book(id, request, response):
    """Get a single book by ID. Returns 404 if not found."""
    book = next((b for b in books if b["id"] == id), None)

    if book is None:
        return response.json({"error": f"Book with id {id} not found"}, 404)

    return response.json(book)


@post("/api/books")
async def create_book(request, response):
    """Create a new book from the JSON body. Returns 201 on success."""
    title = request.body.get("title", "")
    author = request.body.get("author", "")
    year = request.body.get("year", 0)

    if not title or not author:
        return response.json({"error": "title and author are required"}, 400)

    new_book = {
        "id": max(b["id"] for b in books) + 1,
        "title": title,
        "author": author,
        "year": year
    }
    books.append(new_book)

    return response.json(new_book, 201)

Test it:

# List all books
curl http://localhost:7145/api/books

# Filter by author
curl "http://localhost:7145/api/books?author=gibson"

# Sort by year
curl "http://localhost:7145/api/books?sort=year"

# Get a single book
curl http://localhost:7145/api/books/2

# Get a book that does not exist (returns 404)
curl http://localhost:7145/api/books/99

# Create a new book
curl -X POST http://localhost:7145/api/books \
  -H "Content-Type: application/json" \
  -d '{"title": "Foundation", "author": "Isaac Asimov", "year": 1951}'

This example covers every building block the exercises use: reading query parameters, reading path parameters, reading the request body, returning JSON with different status codes, and handling missing data. Refer back to it as you work through the exercises below.

---

10. Exercise: Greeting API + Product List Template

Build the following two features from scratch, without looking at the examples above.

Exercise Part A: Greeting API

Create an API endpoint at GET /api/greet that:

1. Accepts a query parameter name (e.g., /api/greet?name=Sarah)
2. If name is missing, defaults to "Stranger"
3. Returns JSON like:

{
  "greeting": "Welcome, Sarah!",
  "time_of_day": "afternoon"
}

4. The time_of_day should be calculated from the server's current hour:
   • 5:00 - 11:59 = "morning"
   • 12:00 - 16:59 = "afternoon"
   • 17:00 - 20:59 = "evening"
   • 21:00 - 4:59 = "night"

Test your endpoint with:

curl "http://localhost:7145/api/greet?name=Sarah"
curl "http://localhost:7145/api/greet"

Exercise Part B: Product List Page

Create a page at GET /store that:

1. Displays a list of at least 5 products (hardcoded for now)
2. Each product has: name, category, price, and a boolean featured flag
3. Featured products get a visual highlight (different background color, border, or badge)
4. The page shows the total number of products and the number of featured products
5. Uses template inheritance -- a layout template and a page template that extends it
6. Includes tina4.css and frond.js

Your products data should look like this in your route handler:

products = [
    {"name": "Espresso Machine", "category": "Kitchen", "price": 299.99, "featured": True},
    {"name": "Yoga Mat", "category": "Fitness", "price": 29.99, "featured": False},
    {"name": "Standing Desk", "category": "Office", "price": 549.99, "featured": True},
    {"name": "Noise-Canceling Headphones", "category": "Electronics", "price": 199.99, "featured": True},
    {"name": "Water Bottle", "category": "Fitness", "price": 24.99, "featured": False}
]

Expected browser output:

• A page titled "Our Store"
• Text showing "5 products, 3 featured"
• A list of product cards with name, category, price, and a "Featured" badge on highlighted items
• Featured products have a distinct visual style (your choice -- different border color, background, star icon, etc.)

---

11. Solutions

Solution A: Greeting API

Create src/routes/greet.py:

from tina4_python.core.router import get

@get("/api/greet")
async def greet(request, response):
    name = request.params.get("name", "Stranger")

    from datetime import datetime
    hour = datetime.now().hour

    if 5 <= hour < 12:
        time_of_day = "morning"
    elif 12 <= hour < 17:
        time_of_day = "afternoon"
    elif 17 <= hour < 21:
        time_of_day = "evening"
    else:
        time_of_day = "night"

    return response.json({
        "greeting": f"Welcome, {name}!",
        "time_of_day": time_of_day
    })

Test:

curl "http://localhost:7145/api/greet?name=Sarah"

{"greeting":"Welcome, Sarah!","time_of_day":"afternoon"}

curl "http://localhost:7145/api/greet"

{"greeting":"Welcome, Stranger!","time_of_day":"afternoon"}

Solution B: Product List Page

Create src/templates/store-layout.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{% block title %}Store{% endblock %}</title>
    <link rel="stylesheet" href="/css/tina4.css">
    <style>
        body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; margin: 0; padding: 0; background: #f5f5f5; }
        .container { max-width: 960px; margin: 0 auto; padding: 20px; }
        header { background: #1a1a2e; color: white; padding: 16px 20px; }
        header h1 { margin: 0; }
        .stats { color: #888; margin: 8px 0 20px; }
        .product-grid { display: grid; gap: 16px; }
        .product-card { background: white; border: 2px solid #e0e0e0; border-radius: 8px; padding: 16px; }
        .product-card.featured { border-color: #ffc107; background: #fffdf0; }
        .product-name { font-size: 1.2em; font-weight: bold; margin: 0 0 4px; }
        .product-category { color: #666; font-size: 0.9em; }
        .product-price { color: #2d8f2d; font-weight: bold; font-size: 1.1em; margin-top: 8px; }
        .featured-badge { background: #ffc107; color: #333; padding: 2px 8px; border-radius: 4px; font-size: 0.8em; font-weight: bold; }
    </style>
</head>
<body>
    <header>
        <h1>{% block header %}Store{% endblock %}</h1>
    </header>
    <div class="container">
        {% block content %}{% endblock %}
    </div>
    <script src="/js/frond.js"></script>
</body>
</html>

Create src/templates/store.html:

{% extends "store-layout.html" %}

{% block title %}Our Store{% endblock %}
{% block header %}Our Store{% endblock %}

{% block content %}
    <p class="stats">{{ products | length }} products, {{ featured_count }} featured</p>

    <div class="product-grid">
        {% for product in products %}
            <div class="product-card{{ ' featured' if product.featured else '' }}">
                <p class="product-name">
                    {{ product.name }}
                    {% if product.featured %}
                        <span class="featured-badge">Featured</span>
                    {% endif %}
                </p>
                <p class="product-category">{{ product.category }}</p>
                <p class="product-price">${{ "%.2f"|format(product.price) }}</p>
            </div>
        {% endfor %}
    </div>
{% endblock %}

Create src/routes/store.py:

from tina4_python.core.router import get

@get("/store")
async def store_page(request, response):
    products = [
        {"name": "Espresso Machine", "category": "Kitchen", "price": 299.99, "featured": True},
        {"name": "Yoga Mat", "category": "Fitness", "price": 29.99, "featured": False},
        {"name": "Standing Desk", "category": "Office", "price": 549.99, "featured": True},
        {"name": "Noise-Canceling Headphones", "category": "Electronics", "price": 199.99, "featured": True},
        {"name": "Water Bottle", "category": "Fitness", "price": 24.99, "featured": False}
    ]

    featured_count = sum(1 for p in products if p["featured"])

    return response.render("store.html", {
        "products": products,
        "featured_count": featured_count
    })

Open http://localhost:7145/store in your browser. You should see:

• A dark header reading "Our Store"
• Text showing "5 products, 3 featured"
• Five product cards in a grid
• Three cards (Espresso Machine, Standing Desk, Noise-Canceling Headphones) have a yellow border, light yellow background, and a "Featured" badge
• Two cards (Yoga Mat, Water Bottle) have a standard white background with gray border
• Each card shows the product name, category, and price formatted with two decimal places

---

12. Gotchas

1. File not auto-discovered

Problem: You created a route file but nothing happens when you visit the URL.

Cause: The file is not in src/routes/. It must be inside src/routes/ (or a subdirectory), and the file must end with .py.

Fix: Move the file to src/routes/your-file.py and restart the server.

2. Missing import

Problem: NameError: name 'get' is not defined or similar.

Cause: You forgot to import the route decorator.

Fix: Start your route file with the correct import: from tina4_python.core.router import get, post (include whichever decorators you need).

3. Handler not async

Problem: Your route handler runs but returns an error about a coroutine object.

Cause: You defined the handler with def instead of async def. Tina4 Python expects all route handlers to be async.

Fix: Change def greeting(request, response): to async def greeting(request, response):. Every route handler must be async def.

4. Template not found

Problem: Template "my-page.html" not found error.

Cause: The template file is not in src/templates/, or there is a typo in the filename.

Fix: Check that the file exists at src/templates/my-page.html. The name in response.render() is relative to src/templates/.

5. Port already in use

Problem: Error: Address already in use (port 7145)

Cause: Another process (or another Tina4 instance) is using port 7145.

Fix: Stop the other process, or change the port with the CLI flag:

tina4 serve --port 8080

The CLI will also auto-increment the port if it detects the default port is in use.

6. Changes not reflected

Problem: You edited a file but the browser shows the old version.

Cause: Live reload may not be active. Browser caching can serve stale versions.

Fix: Hard-refresh the browser (Ctrl+Shift+R or Cmd+Shift+R). If that fails, restart the dev server with Ctrl+C and tina4 serve.

7. .env not loaded

Problem: Environment variables have no effect.

Cause: The .env file must be at the project root (same directory as pyproject.toml). A subdirectory placement hides it from Tina4.

Fix: Move .env to the project root.