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api.txt
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changelog.txt
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extensions.txt
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faq.txt
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index.txt
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integration.txt
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intro.txt
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latexindex.txt
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sandbox.txt
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switching.txt
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templates.txt
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tricks.txt
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Editing: tricks.txt
Tips and Tricks =============== .. highlight:: html+jinja This part of the documentation shows some tips and tricks for Jinja2 templates. .. _null-master-fallback: Null-Master Fallback -------------------- Jinja2 supports dynamic inheritance and does not distinguish between parent and child template as long as no `extends` tag is visited. While this leads to the surprising behavior that everything before the first `extends` tag including whitespace is printed out instead of being igored, it can be used for a neat trick. Usually child templates extend from one template that adds a basic HTML skeleton. However it's possible put the `extends` tag into an `if` tag to only extend from the layout template if the `standalone` variable evaluates to false which it does per default if it's not defined. Additionally a very basic skeleton is added to the file so that if it's indeed rendered with `standalone` set to `True` a very basic HTML skeleton is added:: {% if not standalone %}{% extends 'master.html' %}{% endif -%} <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <title>{% block title %}The Page Title{% endblock %}</title> <link rel="stylesheet" href="style.css" type="text/css"> {% block body %} <p>This is the page body.</p> {% endblock %} Alternating Rows ---------------- If you want to have different styles for each row of a table or list you can use the `cycle` method on the `loop` object:: <ul> {% for row in rows %} <li class="{{ loop.cycle('odd', 'even') }}">{{ row }}</li> {% endfor %} </ul> `cycle` can take an unlimited amount of strings. Each time this tag is encountered the next item from the list is rendered. Highlighting Active Menu Items ------------------------------ Often you want to have a navigation bar with an active navigation item. This is really simple to achieve. Because assignments outside of `block`\s in child templates are global and executed before the layout template is evaluated it's possible to define the active menu item in the child template:: {% extends "layout.html" %} {% set active_page = "index" %} The layout template can then access `active_page`. Additionally it makes sense to defined a default for that variable:: {% set navigation_bar = [ ('/', 'index', 'Index'), ('/downloads/', 'downloads', 'Downloads'), ('/about/', 'about', 'About') ] -%} {% set active_page = active_page|default('index') -%} ... <ul id="navigation"> {% for href, id, caption in navigation_bar %} <li{% if id == active_page %} class="active"{% endif %}><a href="{{ href|e }}">{{ caption|e }}</a></li> {% endfor %} </ul> ... .. _accessing-the-parent-loop: Accessing the parent Loop ------------------------- The special `loop` variable always points to the innermost loop. If it's desired to have access to an outer loop it's possible to alias it:: <table> {% for row in table %} <tr> {% set rowloop = loop %} {% for cell in row %} <td id="cell-{{ rowloop.index }}-{{ loop.index }}>{{ cell }}</td> {% endfor %} </tr> {% endfor %} </table>
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