qlat_utils.tempita — Tempita Template Substitution

Source: qlat-utils/qlat_utils/tempita.py

Note: Update this document when updating the source file.

Outline

  1. Overview

  2. Usage

  3. Examples

Overview

The qlat_utils.tempita module is a command-line utility for code generation using Tempita template substitution, as bundled with Cython.

It reads a Tempita template file, performs {{expr}} substitution via Cython.Tempita.sub, and writes the result to an output file. This is used internally by the qlat build system to generate C++ / Cython source files from parameterized templates.

The module is a standalone script (not an importable library). It takes exactly two positional arguments — the input template path and the output file path.

Usage

python -m qlat_utils.tempita <template> <output>

Argument

Description

template

Path to the Tempita template file

output

Path to write the generated output

The template file is read as UTF-8, substituted, and the result is written as UTF-8.

Template Syntax

Tempita uses {{expression}} for inline substitution. Any Python expression inside {{ }} is evaluated and its result is inserted into the output. For full Tempita syntax (conditionals, loops, inheritance), see the Cython Tempita documentation.

Examples

Basic Template Substitution

Given a template file header.hpp.tempita:

// Auto-generated — do not edit
#pragma once

constexpr int NDIM = {{ndim}};
constexpr double BETA = {{beta}};

Running:

python -m qlat_utils.tempita header.hpp.tempita header.hpp

produces header.hpp with the {{ndim}} and {{beta}} placeholders replaced by their substituted values.

Build System Integration

In a Makefile or Meson build step, the module is typically invoked as:

python -m qlat_utils.tempita template.pyx.tempita template.pyx

This pattern is used throughout the qlat codebase to generate Cython .pyx and C++ .hpp files from parameterized templates.