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layout: post title: Use Jinja to create gazebo sdf files categories: gazebo tags: [vscode, gazebo, jinja, sdf]

Jinja 101

Jinja2 is a template engine

Install

pip install Jinja2

Syntax

{{ }} Print and Evaluate an expression
{% %} Statement
{# #} Comments

Set variable

{% set title='hello world' %}
{{ title }}

Control

• for loop

{% set names = ['a', 'b', 'c']%}
{% for name in names %}
    {{ loop.index }}: {{name}}
{% endfor %}

# Output result

    1: a

    2: b

    3: c

Variable	Desc
loop.index	index loop start with 1
loop.index0	index loop

• if statment

{% set name='' %}
{% if name %}
    {{ name }}
{% else %}
    no name enter
{% endif %}

White space control

use + and - are control whitespace

• Run the loop example with hyphen at the end of line

{% set names = ['a', 'b', 'c'] -%}
{% for name in names -%}
    {{ loop.index }}: {{name}}
{% endfor -%}

# same output without line spaces
1: a
2: b
3: c

Macro

{%- macro box(x, y, z) -%}
<geometry>
  <box>
    <size>{{x}} {{y}} {{z}}</size>
  </box>
</geometry>
{%- endmacro -%}

# Call the macro
{{ box(1,1,1) }}

CLI for Jinja2

A CLI interface to Jinja2

• install

sudo pip install jinja2-cli

• usage

Usage: jinja2 [options] <input template> <input data>

Demos

• Template

{% if foo is defined -%}
    foo difined and has value: define {{ foo }}
{% endif -%}

• Test

jinja2 -D foo=foo_value hello.txt.jinja

# result
foo difined and has value: define foo_value

Tips

• Install vscode ext for better syntax color

Reference

• Basics of Jinja Template Language