haitch 0.8.0

A lazy HTML element builder.

A lazy HTML element builder.

haitch

alternative pronunciation for the letter "H"

The haitch library provides a builder for composing HTML elements together. The element nodes are functional and will only be rendered when __str__ is invoked.

Why write your HTML in templates when you can do it in Python?

Features

• Compose HTML elements.
• Lazily evaluate DOM tree.
• 100% test coverage.
• 100% type annotated codebase.
• Zero dependencies.
• Document common elements.

Roadmap

• Document all HTML elements from MDN Web Docs.
• Support common third-party plugins like htmx and alpine.

Requirements

Python 3.8+

Quickstart

Install haitch using pip:

$ pip install haitch

Import the library like so:

import haitch as H

By importing the root module, you now have access to any element you want:

# Render known `h1` tag.
h1 = H.h1("Hello, world")
print(h1) # <h1>Hello, world</h1>

# Render custom `foo` tag (useful for web components).
foo = H.foo("Hello, world")
print(foo) # <foo>Hello, world!</foo>

Here is a simple, real-world example that showcases the advantage of writing HTML in Python. Let's say we want a list of customer emails based on some business logic:

# Fetch customers from a data store.
customers = [
    ("[e-mail]", False, True),
    ("[e-mail]", True, False),
    ("[e-mail]", True, False),
    ("[e-mail]", False, False),
]

# Build the DOM tree with attributes and children.
dom = H.div(class_="container")(
    H.h1("Customers to contact:"),
    H.ul(id_="email-customer-list")(
        H.li(H.a(href=f"mailto:{email}")(email))
        for email, is_premium, is_new in customers
        if is_premium or is_new
    ),
)

print(dom)
# <div class="container">
#   <h1>Customers to contact:</h1>
#   <ul id="email-customer-list">
#     <li><a href="mailto:[e-mail]">[e-mail]</a></li>
#     <li><a href="mailto:[e-mail]">[e-mail]</a></li>
#     <li><a href="mailto:[e-mail]">[e-mail]</a></li>
#   </ul>
# </div>

The printed output above is prettified for better readability. The actual output is a minified string with no formatting.

Motivation

Inspired by the fantastic htbuilder library as an alternative to template engines. The library met most of my needs, but I really wanted to expand its functionality by leveraging modern Python features like typing. This coincided with my excitement for Hypermedia-Driven Applications (HDAs) with tools like htmx and alpine.

While writing HDAs has simplified my application logic, the lack of autocompletion and diagnostics in templates are quite annoying. Therefore, my goal with this package is to make writing HTML as simple and fun as writing normal Python code by writing normal Python code.

Non-goals

The following features will not be supported:

• Deprecated elements and attributes: if you want to use them, that is fine by me as haitch supports generic elements and attributes. However, I am not going to write the annotations and documentation for them.
• 100% input validation: this library is meant to assist the developer to write valid HTML with the help of type annotations and documentation. In the end, it is up to the developer and browser to verify that the input is of the correct type. So for example, I will not add any validation to make sure that a <col> element is directly nested inside of a <colgroup> element or that the span attribute for the <col> element is a positive integer.

License

haitch is distributed under the terms of the BSD-3-Clause license.