3.A] Explain Basic Template Tags and Filters.
Answer:
Template Tags
Template Tags: Used for controlling the flow and logic in templates. They perform actions such as conditionals, loops, and including other templates.
{% if %}: Conditional Rendering
Purpose: Renders content based on a condition.
Example:
{% if user.is_authenticated %}
<p>Welcome, {{ user.username }}!</p>
{% else %}
<p>Please log in.</p>
{% endif %}
Explanation: Displays a welcome message if the user is authenticated; otherwise, it prompts the user to log in.
2. {% for %}: Looping
Purpose: Iterates over a list or queryset and renders content for each item.
Example:
<ul>
{% for item in items %}
<li>{{ item.name }}</li>
{% endfor %}
</ul>
Explanation: Loops through the items list and creates a list item (<li>) for each item.
3. {% include %}: Including Templates
Purpose: Includes another template within the current template.
Example:
{% include 'header.html' %}
Explanation: Inserts the content of header.html into the current template.
4. {% block %}: Template Inheritance
Purpose: Defines a block that can be overridden in child templates.
Example:
<!-- base.html -->
<!DOCTYPE html>
<html>
<head>
<title>{% block title %}My Site{% endblock %}</title>
</head>
<body>
{% block content %}{% endblock %}
</body>
</html>
Explanation: Provides a structure for templates. home.html can extend this and override the title and content blocks.
5. {% url %}: Reverse URL Resolution
Purpose: Generates a URL for a given view name.
Example:
<a href="{% url 'view_name' %}">Go to view</a>
Explanation: Generates the URL for the view named 'view_name', which is useful for avoiding hard-coded URLs.
Template Filters
Template Filters: Used for modifying the appearance of variables. They format data, such as changing case, formatting dates, and providing default values.
{{ value|lower }}: Convert to Lowercase
Purpose: Converts text to lowercase.
Example:
{{ message|lower }}
Explanation: Displays the message in all lowercase letters.
2. {{ value|date:"F j, Y" }}: Format Date
Purpose: Formats a date according to a specified format.
Example:
{{ some_date|date:"F j, Y" }}
Explanation: Displays some_date in a format like “August 7, 2024”.
3. {{ value|default:"default value" }}: Default Value
Purpose: Provides a default value if the original value is empty.
Example:
{{ user.name|default:"Anonymous" }}
Explanation: Displays "Anonymous" if user.name is not available or is empty.
4. {{ value|length }}: Length of List or String
Purpose: Gets the length of a list or string.
Example:
{{ my_list|length }}
Explanation: Displays the number of items in my_list or the length of a string
5. {{ value|safe }}: Mark as Safe HTML
Purpose: Marks a string as safe for HTML output.
Example:
{{ safe_html|safe }}
Explanation: Renders safe_html as HTML without escaping it. Use with caution to avoid XSS vulnerabilities.