What is the Jinja2 method for converting a boolean to lowercase?

In Jinja2, there isn't a direct method to convert a boolean value to a lowercase string representation. Boolean values in Jinja2 are treated as their native Python boolean equivalents, True or False. If you need a lowercase string ("true" or "false"), you have to use other techniques such as custom filters, inline if conditions, or type conversion.

Let's look at a few methods to achieve that:

1. Using an inline 'if' condition:

This is one of the simplest ways to handle it:

{{ my_boolean_variable | ternary('true', 'false') }}

or another variant:

{{ 'true' if my_boolean_variable else 'false' }}

Here, my_boolean_variable is evaluated and if it's true the template will output the string 'true', if it is false the output will be 'false'.

2. Using a Custom Filter:

You can define a custom filter that converts a boolean to lowercase strings:

First, register a custom filter in your Python code (assuming Flask here):

from flask import Flask app = Flask(__name__) def bool_to_lower(value): return str(value).lower() app.jinja_env.filters['bool_to_lower'] = bool_to_lower

In template

{{ my_boolean_variable | bool_to_lower }}

Here bool_to_lower converts the boolean into string, and the 'lower()' method is applied for to ensure the output is lowercased ('true' or 'false').

3. String Formatting

You could also cast the boolean to a string then make it lowercase:

{{ "%s" | format(my_boolean_variable) | lower }}

It is important to understand, that in Jinja2 itself there is not function to achieve exactly that. You can achieve it by either adding the needed logic or defining a new filter.

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