ustache

Mustache for Python.

Documentation: ustache.readthedocs.io

Installation

pip install ustache

Usage

Python:

import ustache

print(ustache.render('Hello {{v}}', {'v': 'World!'}))
# Hello World!

Command line:

$ ustache -j data.json -o output.html template.mustache

Highlights

• The fastest pure-python Mustache implementation to this date.

• Command line interface.

• Spec compliant, but also highly compatible with Mustache.js.

• Small codebase, efficiently rendering to str or bytes, supporting streaming.

• Fully customizable behavior: property getter, partial resolver, stringification, escaping and lambdas.

• No dynamic code generation, jit and transpiler friendly.

Considerations

For inter-compatibility with JavaScript (especially Mustache.js, enabling client-side rendering with the same templates), ustache exposes some atypical behavior:

• Mustache blocks stick to JavaScript truthyness (Mustache.js truthyness emulation):

  • Empty mappings (such as dict) are inconditionally truthy.

  • NaN/-NaN are falsy.

• Mustache blocks loop through any iterable other than mappings and strings (Mustache.js Array handling).

• Non-mapping sized objects will expose a virtual length property (JavaScript Array.length emulation, customizable via getter parameter).

• Mapping keys containing dot (.) or whitespace ( ) are unreachable, (Mustache.js property limitation, customizable via getter parameter).

• Sequence elements are accessible by positive index in the same way mapping integer-keyed items are also accessible when no string key conflicts, as properties (JavaScript Object emulation, customizable via getter parameter).

Syntax

Check out the mustache(5) manual.

For quick reference, here is a quick overview of the Mustache syntax.

Template (template.mustache):

{{!comment}}
<ul>
{{#object}}<li>{{property}}</li>{{/object}}
{{^object}}<li>As <b>object</b> is truthy, this won't be shown</li>{{/object}}
{{^null}}<li><b>null</b> is falsy</li>{{/null}}
{{#array}}<li>{{property}}</li>
{{/array}}
{{^array}}<li>Array isn't empty, this won't be shown.</li>{{/array}}
{{#empty_array}}<li>Empty Array, this won't be shown</li>{{/empty_array}}
{{^empty_array}}<li>empty_array is empty</li>{{/empty_array}}
{{&unescaped_html}}
</ul>

Data (data.json):

{
  "object": {
    "property": "Object property value"
  },
  "null": null,
  "array": [
    {"property": "Array item1 property"},
    {"property": "Array item2 property"},
    {"property": "Array item3 property"}
  ],
  "empty_array": [],
  "unescaped_html": "<li>this is unescaped html</li>"
}

Command:

$ ustache -j data.json -o output.html template.mustache

Output:

<ul>
<li>Object property value</li>
<li><b>null</b> is falsy</li>
<li>Array item1 property</li>
<li>Array item2 property</li>
<li>Array item3 property</li>
<li>empty_array is empty</li>
<li>this is unescaped html</li>
</ul>