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269 lines
5.3 KiB
Markdown
269 lines
5.3 KiB
Markdown
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---
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language: Jinja
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contributors:
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- ["Adaías Magdiel", "https://github.com/AdaiasMagdiel"]
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filename: learn-jinja.j2
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---
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## Getting Started with Jinja
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Jinja is a fast, expressive, and extensible templating engine for Python
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applications.
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Jinja includes a lot of functionalities, such as:
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- Template inheritance and inclusion;
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- Defining and importing macros within templates;
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- Security mechanisms to prevent XSS attacks;
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- A sandboxed environment that can safely render untrusted templates;
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- Extensible filters, tests, functions, and even syntax.
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A Jinja template is simply a text file. Jinja doesn't require a specific
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extension, but it's common to use `.j2` or `.jinja` to make it easier for
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some IDEs.
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There are a few kinds of delimiters. The default Jinja delimiters are configured
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as follows:
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- `{% ... %}` for Statements
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- `{{ ... }}` for Expressions to print to the template output
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- `{# ... #}` for Comments not included in the template output
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```jinja
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{# This is an example of a comment. #}
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{#
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You can use this syntax
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to write multiline comments
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as well.
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#}
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```
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## VARIABLES
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```jinja
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{# You have the option to access variables from the context passed to the template #}
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{{ foo }}
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{#
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Additionally, you can use a dot (.) to access attributes of a variable or
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use Python syntax, using []
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#}
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{{ foo.bar }}
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{{ foo['bar'] }}
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{# Within the template, you can define variables as well #}
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{% set name = "Magdiel" %}
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{{ name }}
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```
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## Loops
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```html
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<h1>Members</h1>
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<ul>
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{% for user in users %}
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<li>{{ user.username }}</li>
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{% endfor %}
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</ul>
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<div>
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{% for key, value in my_dict.items() %}
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<p>{{ key }}</p> - <p>{{ value }}</p>
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{% endfor %}
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</div>
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<div>
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{% for idx, url in enumerate(urls) %}
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<a href="{{ url }}">Go to url {{ idx + 1 }}</a>
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{% endfor %}
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</div>
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```
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## Conditionals
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The if statement in Jinja is similar to the if statement in Python. It is
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commonly used to check if a variable is defined, not empty, and not false in
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its most basic form.
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```html
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{% if users %}
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<ul>
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{% for user in users %}
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<li>{{ user.username }}</li>
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{% endfor %}
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</ul>
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{% endif %}
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{# For multiple branches, elif and else can be used like in Python. #}
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{% if message.status == "error" %}
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<p class="text-red-400">{{ message.content }}</p>
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{% elif message.status == "success" %}
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<p class="text-green-400">{{ message.content }}</p>
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{% else %}
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<p class="text-blue-400">{{ message.content }}</p>
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{% endif %}
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```
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## Template Inheritance
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One of the most powerful features of Jinja is template inheritance. You can
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create a base layout with predefined blocks that you can extend in another file
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and override with your own content.
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```html
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{# file: base.html.j2 #}
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<!DOCTYPE html>
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<html lang="en">
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<head>
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{% block head %}
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>{% block title %}{% endblock title %} - Learning Jinja</title>
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{% endblock head %}
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</head>
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<body>
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<main>
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{% block content %}{% endblock %}
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{# the endblock tag doesn't need the name of the block #}
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</main>
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</body>
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</html>
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{# file: child.html.j2 #}
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{% extends "base.html.j2" %}
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{% block head %}
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{{ super() }}
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<script>
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console.log("There's a console.log here")
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</script>
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{% endblock %}
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{% block title %}Home{% endblock %}
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{% block content %}
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<h1>Index</h1>
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<p>Welcome to my home homepage.</p>
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{% endblock %}
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{# RESULT #}
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Home - Learning Jinja</title>
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<script>
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console.log("There's a console.log here")
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</script>
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</head>
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<body>
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<main>
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<h1>Index</h1>
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<p>Welcome to my home homepage.</p>
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</main>
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</body>
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</html>
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```
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### Including Content
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You can include content from another template on your current template using
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the `{% include "template/path" %}` tag.
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```html
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{# file: footer.html.j2 #}
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<footer>
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<p>© 2024 - John Doe</p>
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</footer>
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{# file: index.html.j2 #}
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...
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<body>
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<main>
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<h1>Hi! I'm John Doe!</h1>
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</main>
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{% include "footer.html.j2" %}
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</body>
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...
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{# RESULT #}
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...
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<body>
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<main>
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<h1>Hi! I'm John Doe!</h1>
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</main>
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<footer>
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<p>© 2024 - John Doe</p>
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</footer>
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</body>
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...
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```
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Variables passed to the main template can also be used in the include, as the
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included template has access to the context of the main template.
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```html
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{# file: greetings.html.j2 #}
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<p>I'm the {{ name }} and i like to {{ hobby }}.</p>
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{# file: index.html.j2 #}
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{% set name = "Captain Nemo" %}
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{% set hobby = "navigate through the depths of the ocean" %}
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<div>
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{% include "greetings.html.j2" %}
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</div>
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{# RESULT #}
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<div>
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<p>I'm the Captain Nemo and i like to navigate through the depths of the ocean.</p>
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</div>
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```
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## Macros
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Macros are basically like functions in another languages. You can define macros with or without arguments and reuse them in various parts of your template.
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```html
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{% macro input(value="", type="text", placeholder="") -%}
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<input type="{{ type }}" value="{{ value }}" placeholder="{{ placeholder }}">
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{%- endmacro %}
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<p>{{ input(placeholder="Your username") }}</p>
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<p>{{ input(type="password") }}</p>
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```
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## Official Documentation
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To learn more, access the [official documentation](https://jinja.palletsprojects.com/en/).
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