Bringing component-based design to Django templates.
Why?
Install
Usage Basics
Your First component
Attributes
Named Slots
Pass Template Variables
Template expressions in attributes
Boolean attributes
Passing Python data types
Increase Re-usability with {{ attrs }}
Merging and Proxying Attributes with :attrs
In-component Variables with <c-vars>
HTMX Example
Limitations in Django that Cotton overcomes
Configuration
Caching
Tools
Version support
Changelog
Comparison with other packages
Cotton aims to overcome certain limitations that exist in the django template system that hold us back when we want to apply modern practices to compose UIs in a modular and reusable way.
pip install django-cotton
INSTALLED_APPS = [
'django_cotton'
]
If you have previously specified a custom loader, you should perform manual setup.
templates/cotton folder (or define a custom folder).my_component.html<c-my-component /><!-- cotton/button.html -->
<a href="/" class="...">{{ slot }}</a>
<!-- in view --> <c-button>Contact</c-button>
<!-- html output --> <a href="/" class="...">Contact</a>
Everything provided between the opening and closing tag is provided to the component as {{ slot }}. It can contain any content, HTML or Django template expression.
<!-- cotton/button.html -->
<a href="{{ url }}" class="...">
{{ slot }}
</a>
<!-- in view --> <c-button url="/contact">Contact</c-button>
<!-- html output -->
<a href="/contact" class="...">
Contact
</a>
Named slots are a powerful concept. They allow us to provide HTML to appear in one or more areas in the component. Here we allow the button to optionally display an svg icon:
<!-- cotton/button.html -->
<a href="{{ url }}" class="...">
{{ slot }}
{% if icon %}
{{ icon }}
{% endif %}
</a>
<!-- in view -->
<c-button url="/contact">
Contact
<c-slot name="icon">
<svg>...</svg>
</c-slot>
</c-button>
Named slots can also contain any html or django template expression:
<!-- in view -->
<c-button url="/contact">
<c-slot name="icon">
{% if mode == 'edit' %}
<svg id="pencil">...</svg>
{% else %}
<svg id="disk">...</svg>
{% endif %}
</c-slot>
</c-button> Pass template variable as an attribute
To pass a template variable you prepend the attribute name with a colon :. Consider a bio card component:
<!-- in view --> <c-bio-card :user="user" />
That has a component definition like:
<!-- cotton/bio_card.html -->
<div class="...">
<img src="{{ user.avatar }}" alt="...">
{{ user.username }} {{ user.country_code }}
</div> Template expressions inside attributes
You can use template expression statements inside attributes.
<c-weather icon="fa-{{ icon }}"
unit="{{ unit|default:'c' }}"
condition="very {% get_intensity %}"
/>
Boolean attributes reduce boilerplate when we just want to indicate a certain attribute should be True or not.
<!-- in view --> <c-button url="/contact" external>Contact</c-button>
By passing just the attribute name without a value, it will automatically be provided to the component as True
<!-- cotton/button.html -->
<a href="{{ url }}" {% if external %} target="_blank" {% endif %} class="...">
{{ slot }}
</a> Passing Python data types
Using the ':' to prefix an attribute tells Cotton we're passing a dynamic type down. We already know we can use this to send a variable, but you can also send basic python types, namely:
This benefits a number of use-cases, for example if you have a select component that you want to provide the possible options from the parent:
<!-- cotton/select.html -->
<select {{ attrs }}>
{% for option in options %}
<option value="{{ option }}">{{ option }}</option>
{% endfor %}
</select>
<c-select name="q1" :options="['yes', 'no', 'maybe']" />
<!-- source code output -->
<select name="q1">
<option value="yes">yes</option>
<option value="no">no</option>
<option value="maybe">maybe</option>
</select> Increase Re-usability with {{ attrs }}
{{ attrs }} is a special variable that contains all the attributes passed to the component in an key="value" format. This is useful when you want to pass all attributes to a child element without having to explicitly define them in the component template. For example, you have inputs that can have any number of attributes defined:
<!-- cotton/input.html -->
<input type="text" class="..." {{ attrs }} />
<!-- example usage --> <c-input placeholder="Enter your name" /> <c-input name="country" id="country" value="Japan" required />
<!-- html output --> <input type="text" class="..." placeholder="Enter your name" /> <input type="text" class="..." name="country" id="country" value="Japan" required />Merging and Proxying Attributes with
:attrs
While {{ attrs }} is great for outputting all attributes passed to a component, Cotton provides more control with the special dynamic attribute :attrs.
Merge a dictionary of attributes
You can pass a dictionary of attributes (e.g., from your Django view's context) to a component using the :attrs syntax. These attributes are then merged with any other attributes passed directly and become available in the component's attrs variable (for use with {{ attrs }}). This is useful for applying a pre-defined set of attributes.
<!-- cotton/input.html -->
<input type="text" {{ attrs }} />
# In your view context
context = {
'widget_attrs': {
'placeholder': 'Enter your name',
'data-validate': 'true',
'size': '40'
}
}
<!-- In your template (e.g., form_view.html) --> <c-input :attrs="widget_attrs" required />
<!-- HTML output --> <input type="text" placeholder="Enter your name" data-validate="true" size="40" required />
Notice how required (passed directly to <c-input>) is merged with attributes from widget_attrs.
Proxy attributes to a nested component
The :attrs attribute also allows you to pass all attributes received by a wrapper component directly to a nested component. This is powerful for creating higher-order components or wrapping existing ones. When you use <c-child :attrs="attrs">, the child component receives the attrs dictionary of the parent.
<!-- cotton/outer_wrapper.html -->
<c-vars message /> <!-- 'message' is for outer_wrapper, not to be passed via attrs -->
<p>Outer message: {{ message }}</p>
<c-inner-component :attrs="attrs">
{{ slot }}
</c-inner-component>
<!-- cotton/inner_component.html -->
<div class="inner {{ class }}">
{{ slot }}
</div>
<!-- In view -->
<c-outer-wrapper message="Hello from outside"
class="special-class">
Inner content
</c-outer-wrapper>
<!-- HTML output -->
<p>Outer message: Hello from outside</p>
<div class="inner special-class">
Inner content
</div>
Attributes like class are passed from <c-outer_wrapper> to <c-inner_component> via its attrs variable, while message (declared in <c-vars>) is used by outer-wrapper itself and excluded from the attrs passed down.
<c-vars>
Django templates adhere quite strictly to the MVC model and does not permit a lot of data manipulation in views. Fair enough, but what if we want to handle data for the purpose of UI state only? Having presentation related variables defined in the back is overkill and can quickly lead to higher maintenance cost and loses encapsulation of the component. Cotton allows you define in-component variables for the following reasons:
Using<c-vars> for default attributes
In this example we have a button component with a default "theme" but it can be overridden.
<!-- cotton/button.html -->
<c-vars theme="bg-purple-500" />
<a href="..." class="{{ theme }}">
{{ slot }}
</a>
<!-- in view --> <c-button>I'm a purple button</c-button>
<!-- html output -->
<a href="..." class="bg-purple-500">
I'm a purple button
</a>
Now we have a default theme for our button, but it is overridable:
<!-- in view --> <c-button theme="bg-green-500">But I'm green</c-button>
<!-- html output -->
<a href="..." class="bg-green-500">
But I'm green
</a> Using <c-vars> to govern {{ attrs }}
Using {{ attrs }} to pass all attributes from parent scope onto an element in the component, you'll sometimes want to provide additional properties to the component which are not intended to be an attributes. In this case you can declare them in <c-vars /> and it will prevent it from being in {{ attrs }}
Take this example where we want to provide any number of attributes to an input but also an icon setting which is not intened to be an attribute on <input>:
<!-- in view --> <c-input type="password" id="password" icon="padlock" />
<!-- cotton/input.html -->
<c-vars icon />
<img src="icons/{{ icon }}.png" />
<input {{ attrs }} />
Input will have all attributes provided apart from the icon:
<input type="password" id="password" />
Sometimes there is a need to include a component dynamically, for example, you are looping through some data and the type of component is defined within a variable.
<!--
form_fields = [
{'type': 'text'},
{'type': 'textarea'},
{'type': 'checkbox'}
]
-->
{% for field in form_fields %}
<c-component :is="field.type" />
{% endfor %}
You can also provide a template expression, should the component be inside a subdirectory or have a prefix:
{% for field in form_fields %}
<!-- subfolder -->
<c-component is="form-fields.{{ field.type }}" />
<!-- component prefix -->
<c-component is="field_{{ field.type }}" />
{% endfor %}
Cotton helps carve out re-usable components, here we show how to make a re-usable form, reducing code repetition and improving maintainability:
<!-- cotton/form.html -->
<div id="result" class="..."></div>
<form {{ attrs }} hx-target="#result" hx-swap="outerHTML">
{{ slot }}
<button type="submit">Submit</button>
</form>
<!-- in view -->
<c-form hx-post="/contact">
<input type="text" name="name" placeholder="Name" />
<input type="text" name="email" placeholder="Email" />
<input type="checkbox" name="signup" />
</c-form>
<c-form hx-post="/buy">
<input type="text" name="type" />
<input type="text" name="quantity" />
</c-form> Limitations in Django that Cotton overcomes
Whilst you can build frontends with Django’s native tags, there are a few things that hold us back when we want to apply modern practices:
{% block %} and {% extends %}
This system strongly couples child and parent templates making it hard to create a truly re-usable component that can be used in places without it having a related base template.
What about{% include %} ?
Modern libraries allow components to be highly configurable, whether it’s by attributes, passing variables, passing HTML with default and named slots. {% include %} tags, whilst they have the ability to pass simple variables and text, they will not allow you to easily send HTML blocks with template expressions let alone other niceties such as boolean attributes, named slots etc.
Whilst {% with %} tags allow us to provide variables and strings it quickly busies up your code and has the same limitations about passing more complex types.
Custom{% templatetags %}
Cotton does essentially compile down to templatetags but there is some extra work it performs above it to help with scoping and auto-managing keys which will be difficult to manage manually in complex nested structures.
Native Django template tags vs CottonIn addition, Cotton enables you to navigate around some of the limitations with Django's native tags and template language:
❌ Django native:
{% my_header icon="<svg>...</svg>" %}
✅ Cotton:
<c-my-header>
<c-slot name="icon">
<svg>...</svg>
</c-slot>
</c-my-header> Template expressions in attributes
❌ Django native:
{% bio name="{{ first_name }} {{ last_name }}" extra="{% get_extra %}" %}
✅ Cotton:
<c-bio name="{{ first_name }} {{ last_name }}" extra="{% get_extra %} />
❌ Django native:
{% my_component default_options="['yes', 'no', 'maybe']" %}
{% my_component config="{'open': True}" %}
{% my_component enabled="True" %}
✅ Cotton:
<c-my-component :default_options="['yes', 'no', 'maybe']" />
<c-my-component :config="{'open': True}" />
<c-my-component :enabled="True" />
(provides a List and Dict to component)
❌ Django native:
✅ Cotton:
<c-my-component
class="blue"
x-data="{
something: 1
}" />
❌ Django native:
{% {{ templatetag_name }} arg=1 %}
✅ Cotton:
<c-component :is="component_name" />
<c-component is="{{ component_name }}" />
<c-component is="subfolder1.subfolder2.{{ component_name }}" />
COTTON_DIR (default: "cotton")
The directory where your components are stored.
COTTON_BASE_DIR (default: None)
If you use a project-level templates folder then you can set the path here. This is not needed if your project already has a BASE_DIR variable.
COTTON_SNAKE_CASED_NAMES (default: True)
Whether to search for component filenames in snake_case. If set to False, you can use kebab-cased / hyphenated filenames.
Cotton is optimal when used with Django's cached.Loader. If you use automatic configuration then the cached loader will be automatically applied.
Notes:
django-expr package. So the list focuses on a comparison of core feature of that library.For full docs and demos, checkout django-cotton.com
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