Metadata-Version: 2.3
Name: tdom
Version: 0.1.17
Summary: A 🤘 rockin' t-string HTML templating system for Python 3.14.
Author: Dave Peck, Ian Wilson, Andrea Giammarchi, Paul Everitt
Author-email: Dave Peck <davepeck@davepeck.org>, Ian Wilson <ian@gardentheory.org>, Andrea Giammarchi <andrea.giammarchi@gmail.com>, Paul Everitt <pauleveritt@me.com>
License: MIT
Classifier: Development Status :: 2 - Pre-Alpha
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: Python :: 3.14
Classifier: Topic :: Internet :: WWW/HTTP :: Dynamic Content
Classifier: Topic :: Text Processing :: Markup :: HTML
Classifier: Typing :: Typed
Requires-Dist: markupsafe>=3.0.3
Requires-Python: >=3.14
Project-URL: Homepage, https://github.com/t-strings/tdom
Project-URL: Changelog, https://github.com/t-strings/tdom/releases
Project-URL: Issues, https://github.com/t-strings/tdom/issues
Project-URL: CI, https://github.com/t-strings/tdom/actions
Description-Content-Type: text/markdown

# tdom

A 🤘 rockin' t-string HTML templating system for Python 3.14.

[![PyPI](https://img.shields.io/pypi/v/tdom.svg)](https://pypi.org/project/tdom/)
[![Tests](https://github.com/t-strings/tdom/actions/workflows/ci.yml/badge.svg)](https://github.com/t-strings/tdom/actions/workflows/ci.yml)
[![Test Count](https://t-strings.github.io/tdom/reports/pytest.svg)](https://t-strings.github.io/tdom/reports/pytest.html)
[![Coverage](https://t-strings.github.io/tdom/reports/coverage.svg)](https://t-strings.github.io/tdom/reports/coverage/index.html)
[![Changelog](https://img.shields.io/github/v/release/t-strings/tdom?include_prereleases&label=changelog)](https://github.com/t-strings/tdom/releases)
[![License](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/t-strings/tdom/blob/main/LICENSE)
[![Docs](https://img.shields.io/badge/docs-online-blue.svg)](https://t-strings.github.io/tdom/)

## NOTE WELL

This is pre-alpha software. It is still under heavy development and the API may change without warning. We would love community feedback to help shape the direction of this project!

## Installation

You'll need [Python 3.14](https://www.python.org/downloads/release/python-3140/), which was released in October 2025.

Then, just run:

```bash
pip install tdom
```

If you have [Astral's `uv`](https://docs.astral.sh/uv/) you can easily try `tdom` in an isolated Python 3.14 environment:

```bash
uv run --with tdom --python 3.14 python
```

## Usage

`tdom` leverages Python 3.14's
[new t-strings feature](https://t-strings.help/introduction.html) to provide a
powerful HTML templating system that feels familiar if you've used JSX, Jinja2,
or Django templates.

T-strings work just like f-strings but use a `t` prefix and
[create `Template` objects](https://docs.python.org/3.14/library/string.templatelib.html#template-strings)
instead of strings.

Once you have a `Template`, you can call this package's `html()` function to
render it to a string.

### Getting Started

Import the `html` function and start creating templates:

```python
from tdom import html
greeting = html(t"<h1>Hello, World!</h1>")
assert greeting == "<h1>Hello, World!</h1>"
```

### Variable Interpolation

Just like f-strings, you can interpolate (substitute) variables directly into
your templates:

```python
name = "Alice"
age = 30
user_info = html(t"<p>Hello, {name}! You are {age} years old.</p>")
assert user_info == "<p>Hello, Alice! You are 30 years old.</p>"
```

The `html()` function ensures that interpolated values are automatically escaped
to prevent XSS attacks:

```python
user_name = "<script>alert('owned')</script>"
safe_output = html(t"<p>Hello, {user_name}!</p>")
assert safe_output == "<p>Hello, &lt;script&gt;alert(&#39;owned&#39;)&lt;/script&gt;!</p>"
```

### Attribute Substitution

The `html()` function provides a number of convenient ways to define HTML
attributes.

#### Direct Attribute Values

You can place values directly in attribute positions:

```python
url = "https://example.com"
link = html(t'<a href="{url}">Visit our site</a>')
assert link == '<a href="https://example.com">Visit our site</a>'
```

You don't _have_ to wrap your attribute values in quotes:

```python
element_id = "my-button"
button = html(t"<button id={element_id}>Click me</button>")
assert button == '<button id="my-button">Click me</button>'
```

Multiple substitutions in a single attribute are supported too:

```python
first = "Alice"
last = "Smith"
button = html(t'<button data-name="{first} {last}">Click me</button>')
assert button == '<button data-name="Alice Smith">Click me</button>'
```

Boolean attributes are supported too. Just use a boolean value in the attribute
position:

```python
form_button = html(t"<button disabled={True} hidden={False}>Submit</button>")
assert form_button == "<button disabled>Submit</button>"
```

#### The `class` Attribute

The `class` attribute has special handling to make it easy to combine multiple
classes from different sources. The simplest way is to provide a list of class
names:

```python
classes = ["btn", "btn-primary", "active"]
button = html(t'<button class="{classes}">Click me</button>')
assert button == '<button class="btn btn-primary active">Click me</button>'
```

The `class` attribute can also be a dictionary to toggle classes on or off:

```python
classes = {"active": True, "btn": True}
button = html(t'<button class={classes}>Click me</button>')
assert button == '<button class="active btn">Click me</button>'
```

The `class` attribute can be specified more than once. The values are merged
from left to right. A common use case would be to update and/or extend default
classes:

```python
classes = {"btn-primary": True, "btn-secondary": False}
button = html(t'<button class="btn btn-secondary" class={classes}>Click me</button>')
assert button == '<button class="btn btn-primary">Click me</button>'
```

#### The `style` Attribute

The `style` attribute has special handling to make it easy to combine multiple
styles from different sources.  The simplest way is to provide a dictionary of
CSS properties and values for the `style` attribute:

```python
# Style attributes from dictionaries
styles = {"color": "red", "font-weight": "bold", "margin": "10px"}
styled = html(t"<p style={styles}>Important text</p>")
assert styled == '<p style="color: red; font-weight: bold; margin: 10px">Important text</p>'
```

Style attributes can also be merged to extend a base style:

```python
add_styles = {"font-weight": "bold"}
para = html(t'<p style="color: red" style={add_styles}>Important text</p>')
assert para == '<p style="color: red; font-weight: bold">Important text</p>'
```

#### The `data` and `aria` Attributes

The `data` and `aria` attributes also have special handling to convert
dictionary keys to the appropriate attribute names:

```python
data_attrs = {"user-id": 123, "role": "admin"}
aria_attrs = {"label": "Close dialog", "hidden": True}
element = html(t"<div data={data_attrs} aria={aria_attrs}>Content</div>")
assert element == '<div data-user-id="123" data-role="admin" aria-label="Close dialog" aria-hidden="true">Content</div>'
```

Note that boolean values in `aria` attributes are converted to `"true"` or
`"false"` as per [the ARIA specification](https://www.w3.org/TR/wai-aria-1.2/).

#### Attribute Spreading

It's possible to specify multiple attributes at once by using a dictionary and
spreading it into an element using curly braces:

```python
attrs = {"href": "https://example.com", "target": "_blank"}
link = html(t"<a {attrs}>External link</a>")
assert link == '<a href="https://example.com" target="_blank">External link</a>'
```

You can also combine spreading with individual attributes:

```python
base_attrs = {"id": "my-link"}
target = "_blank"
link = html(t'<a {base_attrs} target="{target}">Link</a>')
assert link == '<a id="my-link" target="_blank">Link</a>'
```

Special attributes likes `class` behave as expected when combined with
spreading:

```python
classes = {"btn": True, "active": True}
attrs = {"class": classes, "id": "act_now", "data": {"wow": "such-attr"}}
button = html(t'<button {attrs}>Click me</button>')
assert button == '<button class="btn active" id="act_now" data-wow="such-attr">Click me</button>'
```

### Conditional Rendering

You can use Python's conditional expressions for dynamic content:

```python
is_logged_in = True
user_content = t"<span>Welcome back!</span>"
guest_content = t"<a href='/login'>Please log in</a>"
header = html(t"<div>{user_content if is_logged_in else guest_content}</div>")
assert header == '<div><span>Welcome back!</span></div>'
```

Short-circuit evaluation is also supported for conditionally including elements:

```python
show_warning = False
warning = t'<div class="alert">Warning message</div>'
page = html(t"<main>{show_warning and warning}</main>")
assert page == "<main></main>"
```

### Lists and Iteration

Generate repeated elements using list comprehensions:

```python
fruits = ["Apple", "Banana", "Cherry"]
fruit_list = html(t"<ul>{[t'<li>{fruit}</li>' for fruit in fruits]}</ul>")
assert fruit_list == "<ul><li>Apple</li><li>Banana</li><li>Cherry</li></ul>"
```

### Raw HTML Injection

The `tdom` package provides several ways to include trusted raw HTML content in
your templates. This is useful when you have HTML content that you _know_ is
safe and do not wish to escape.

Under the hood, `tdom` builds on top of the familiar
[MarkupSafe](https://pypi.org/project/MarkupSafe/) library to handle trusted
HTML content. If you've used Flask, Jinja2, or similar libraries, this will feel
very familiar.

The `Markup` class from MarkupSafe is available for use:

```python
from tdom import html, Markup

trusted_html = Markup("<strong>This is safe HTML</strong>")
content = html(t"<div>{trusted_html}</div>")
assert content == '<div><strong>This is safe HTML</strong></div>'
```

As a convenience, `tdom` also supports a `:safe` format specifier that marks a
string as safe HTML:

```python
trusted_html = "<em>Emphasized text</em>"
page = html(t"<p>Here is some {trusted_html:safe} content.</p>")
assert page == "<p>Here is some <em>Emphasized text</em> content.</p>"
```

For interoperability with other templating libraries, any object that implements
a `__html__` method will be treated as safe HTML. Many popular libraries
(including MarkupSafe and Django) use this convention:

```python
class SafeWidget:
    def __html__(self):
        return "<button>Custom Widget</button>"

page = html(t"<div>My widget: {SafeWidget()}</div>")
assert page == "<div>My widget: <button>Custom Widget</button></div>"
```

You can also explicitly mark a string as "unsafe" using the `:unsafe` format
specifier. This forces the string to be escaped, even if it would normally be
treated as safe:

```python
from tdom import html, Markup
trusted_html = Markup("<strong>This is safe HTML</strong>")
page = html(t"<div>{trusted_html:unsafe}</div>")
assert page == "<div>&lt;strong&gt;This is safe HTML&lt;/strong&gt;</div>"
```

### Template Composition

You can easily combine multiple templates and create reusable components.

Template nesting is straightforward:

```python
content = t"<h1>My Site</h1>"
page = html(t"<div>{content}</div>")
assert page == "<div><h1>My Site</h1></div>"
```

In the example above, `content` is a `Template` object that gets correctly
parsed and embedded within the outer template. You can also explicitly call
`html()` on nested templates if you prefer:

```python
content = t"<h1>My Site</h1>"
page = html(t"<div>{content}</div>")
assert page == "<div><h1>My Site</h1></div>"
```

The result is the same either way.

#### Component Functions

You can create reusable component functions that generate templates with dynamic
content and attributes. Use these like custom HTML elements in your templates.

The basic form of all component functions is:

```python
from string.templatelib import Template

from typing import Any, Iterable
from tdom import html

def MyComponent(children: Template, **attrs: Any) -> Template:
    return t"<div {attrs}>Cool: {children}</div>"
```

To _invoke_ your component within an HTML template, use the special
`<{ComponentName} ... />` syntax:

```python
result = html(t"<{MyComponent} id='comp1'>Hello, Component!</{MyComponent}>")
assert result == '<div id="comp1">Cool: Hello, Component!</div>'
```

Because attributes are passed as keyword arguments, you can explicitly provide
type hints for better editor support:

```python
from string.templatelib import Template

from typing import Any
from tdom import html

def Link(*, href: str, text: str, data_value: int, children: Template = t'', **attrs: Any) -> Template:
    # Children are ignored.
    return t'<a href="{href}" {attrs}>{text}: {data_value}</a>'

result = html(t'<{Link} href="https://example.com" text="Example" data-value={42} target="_blank" />')
assert result == '<a href="https://example.com" target="_blank">Example: 42</a>'
```

Note that attributes with hyphens (like `data-value`) are converted to
underscores (`data_value`) in the function signature.

Component functions build and return a `Template` that will be processed as if
it were interpolated exactly where the component was invoked.

<!-- invisible-code-block: python
from string.templatelib import Template
-->

```python
def Greeting(name: str) -> Template:
    return t"<span>Hello, {name}!</span>"

result = html(t"Your greeting is <{Greeting} name='Alice' />.")
assert result == "Your greeting is <span>Hello, Alice!</span>."
```

#### Class-based components

Component functions are great for simple use cases, but for more complex
components you may want to use a class-based approach. Remember that the
component invocation syntax (`<{ComponentName} ... />`) works with any callable.
That includes the `__init__` method of a class.  If a callable does not return
a `Template` then it must return another callable that takes no arguments and
returns a `Template`.  That can be done by defining a `__call__` method on
the class.

One particularly useful pattern is to build class-based components with
dataclasses:

```python
from string.templatelib import Template
from dataclasses import dataclass, field
from typing import Any, Iterable
from tdom import html
from textwrap import dedent

@dataclass
class Card:
    children: Template
    title: str
    subtitle: str | None = None

    def __call__(self) -> Template:
        return t"""
            <div class='card'>
                <h2>{self.title}</h2>
                {self.subtitle and t'<h3>{self.subtitle}</h3>'}
                <div class="content">{self.children}</div>
            </div>
        """

result = html(t"<{Card} title='My Card' subtitle='A subtitle'><p>Card content</p></{Card}>")
assert dedent(result) == """
<div class="card">
    <h2>My Card</h2>
    <h3>A subtitle</h3>
    <div class="content"><p>Card content</p></div>
</div>
"""
```

This approach allows you to encapsulate component logic and state within a
class, making it easier to manage complex components.

As a note, `children` are optional in component signatures. If a component
requests children, it will receive them if provided. If no children are
provided, the value of children is an empty `Template`, ie. `t""`. If the
component does _not_ ask for children, but they are provided, then they
are silently ignored.

#### SVG Support

SVG elements work seamlessly with `tdom` since they follow the same XML-like
syntax as HTML. You can create inline SVG graphics by simply including SVG tags
in your templates:

<!-- invisible-code-block: python
from string.templatelib import Template
from tdom import html
-->

```python
icon = html(t"""
    <svg width="24" height="24" viewBox="0 0 24 24" fill="none">
        <circle cx="12" cy="12" r="10" stroke="currentColor" stroke-width="2"/>
        <path d="M12 6v6l4 2" stroke="currentColor" stroke-width="2"/>
    </svg>
""")
assert '<svg width="24" height="24"' in icon
assert '<circle cx="12" cy="12" r="10"' in icon
```

All the same interpolation, attribute handling, and component features work with
SVG elements:

```python
def Icon(*, size: int = 24, color: str = "currentColor") -> Template:
    return t"""
        <svg width="{size}" height="{size}" viewBox="0 0 24 24" fill="none">
            <circle cx="12" cy="12" r="10" stroke="{color}" stroke-width="2"/>
        </svg>
    """

result = html(t'<{Icon} size={48} color="blue" />')
assert 'width="48"' in result
assert 'stroke="blue"' in result
```

#### Context

Unlike some template systems that provide implicit "context" objects for passing
data through component hierarchies, `tdom` embraces Python's explicit approach.
If you need to pass data to nested components, you have several Pythonic
options:

1. **Pass data as explicit arguments**: The most straightforward approach.

2. **Use closures**: Components are just functions, so they can close over
   variables in their enclosing scope:

```python
theme = {"primary": "blue", "spacing": "10px"}

def Button(text: str) -> Template:
    # Button has access to theme from enclosing scope
    return t'<button style="color: {theme["primary"]}; margin: {theme["spacing"]}">{text}</button>'

result = html(t'<{Button} text="Click me" />')
assert 'color: blue' in result
assert 'margin: 10px' in result
assert '>Click me</button>' in result
```

3. **Use module-level or global state**: For truly application-wide
   configuration.

4. **Use a dedicated context library**: Libraries like `contextvars` can
   provide more sophisticated context management if needed.

This explicit approach makes it clear where data comes from and avoids the
"magic" of implicit context passing.

### The `tdom` Module

#### Utilities

The `tdom` package includes several utility functions for working with
interpolations:

**`format_interpolation()`**: This function handles the formatting of
interpolated values according to their format specifiers and conversions. It's
used internally by the `html()` function but can also be used independently:

```python
from string.templatelib import Interpolation
from tdom.format import convert

# Test convert function
assert convert("hello", "s") == "hello"
assert convert("hello", "r") == "'hello'"
assert convert(42, None) == 42
```

**`convert()`**: Applies conversion specifiers (`!a`, `!r`, `!s`) to values
before formatting, following the same semantics as f-strings.

These utilities follow the patterns established by PEP 750 for t-string
processing, allowing you to build custom template processors if needed.

## Contributing

Contributions are welcome! Please feel free to submit issues or pull requests on
[GitHub](https://github.com/t-strings/tdom).
