fstache 0.1.1

Fastest dependency-free, typed Mustache renderer for Python 3.12+

Fstache

Overview

• Dependency-free Mustache renderer for Python 3.12+.
• Supports upstream Mustache spec fixtures, including lambdas and dynamic partial names; inheritance is unsupported.
• Built for speed; benchmarked at 3.3x Chevron, 3.1x mstache, and 3.5x Pystache.
• PEP 561 typed package.
• Supports Python mappings, objects, sequences, and callables as render data.
• Static partials are preloaded and inlined, eliminating render-time boundary overhead.

Benchmarks

Renderer Throughput

Library	Renders per second	Indentation details
Fstache	4066.5	Deviates: ignore_indents=True skips standard standalone partial reindentation.
Fstache	3102.2	Follows standard standalone partial indentation.
mstache	1339.0	Deviates: keep_lines=True keeps tag-only lines instead of collapsing them, so partial indentation is not reapplied to every partial line.
mstache	985.3	Follows standard standalone partial indentation.
Chevron	951.1	Follows standard standalone partial indentation.
Pystache	898.8	Follows standard standalone partial indentation.

Benchmark environment

Field	Value
Python	CPython 3.14.6
OS	Fedora Linux 44 (Workstation Edition), Linux 7.0.12-201.fc44.x86_64
CPU	AMD Ryzen 7 8845HS w/ Radeon 780M Graphics, 8 cores / 16 threads
Compared versions	Fstache 0.1.0, Chevron 0.14.0, mstache 0.3.0, Pystache 0.6.8
Command	RENDERER=<renderer> uv run --python 3.14 --extra dev python tests/perf_test.py <renderer> values: fstache.no_indentation, fstache, mstache.no_indentation, mstache, chevron, pystache

Methodology

• The benchmark renders a realistic, heavy marketing/docs HTML page from the source Mustache templates, JSON data, and perf script:
  • About 100 KiB of rendered HTML (source) from 15 Mustache templates, including 14 partial files.
  • Tailwind CSS v4 utility-heavy markup with Alpine.js attributes, inline SVG icons, responsive navigation, cards, tables, accordions, and form controls.
  • About 15 KiB of JSON context data with nested arrays for navigation, feature cards, testimonials, a recursive docs tree, comparison rows, blog posts, changelog entries, FAQs, and pricing plans.
  • 42 section, inverted-section, and partial references, including 24 section tags for loops and conditionals plus recursive node partial rendering.
• The benchmark isolates render throughput from setup work:
  • Each engine preloads the template files and partials during setup.
  • Each engine uses the closest available precompiled, preparsed, or pretokenized representation for the layout and partials.
  • The timed render loop excludes disk I/O and one-time template preparation.

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Utility Commands

Generate Reference HTML

Builds and renders the templates from ./demo into ./demo/dist/index.html (performing file I/O):

make build-html

Format and Lint

Runs ruff checks and auto-formats the project:

make post-ai-change