nnA boolean literal represents a value that is either true or false. These are fundamental for controlling program flow and logic in your templates. The values `true` and `false` are always lowercase. For consistency with Python and to avoid past confusion, you can also use True and False, but the lowercase versions are generally preferred.nn

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How It Works

nBoolean values are used in conditional statements (e.g., `if`, `elif`, `else`) to determine which parts of a template should be rendered. A condition that evaluates to true will execute the associated code block, while one that evaluates to false will not. These literals are crucial for making dynamic decisions within a template.n

Syntax

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{{ true }}n{{ false }}n{% if my_variable is True %}n    ...n{% endif %}

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Demonstration with Code Samples

nHere are some practical examples of how to use Boolean literals in a Jinja2 application.n

1. Using Booleans in an `if` Statement

nThis is the most common use case for booleans, where you conditionally display content based on a boolean value.nnJinja2 Templaten

{% set is_logged_in = true %}n{% if is_logged_in %}n    <p>Welcome back!</p>n{% else %}n    <p>Please log in to continue.</p>n{% endif %}

nExplanation: The `is_logged_in` variable is set totrue, so the `if` block is executed, displaying the “Welcome back!” message. If it werefalse, the “Please log in…” message would be displayed instead.nn

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2. Setting a Variable to a Boolean

nYou can set a variable directly to a boolean literal to use it later in your template, often in a condition or to display its value.nnJinja2 Templaten

{% set is_active_user = false %}n<p>User status:n{% if is_active_user %}n    Activen{% else %}n    Inactiven{% endif %}n</p>

nExplanation: The variable `is_active_user` is set to `false`. The `if` statement evaluates this and renders the `else` block, resulting in the output “User status: Inactive.”nn

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3. Using Booleans in a Comparison

nYou can also explicitly compare a variable to a boolean literal, though this is often redundant if the variable itself is already a boolean.nnJinja2 Templaten

{% set is_admin = True %}n{% if is_admin == true %}n    <p>You have administrative privileges.</p>n{% endif %}

nExplanation: The `is_admin` variable is compared directly to the `true` literal. Since `True` and `true` are equivalent, the condition passes, and the message is displayed.nn