Template filters in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Flask template filter usage?

Given the Flask template code below, what will be rendered?

{{ 'hello world'|capitalize }}

A Hello world

B Hello World

C HELLO WORLD

D hello world

💡 Hint

The capitalize filter makes only the first letter uppercase and the rest lowercase.

The capitalize filter converts the first character to uppercase and the rest to lowercase. So 'hello world' becomes 'Hello world'.

📝 Syntax

intermediate

Which option correctly applies a custom filter in Flask template?

Assuming a custom filter named reverse_string is registered in Flask, which template syntax correctly applies it to variable name?

A {{ name.reverse_string() }}

B {{ reverse_string(name) }}

C {% reverse_string name %}

D {{ name|reverse_string }}

💡 Hint

Filters in Flask templates use the pipe | symbol.

Custom filters are applied using the pipe syntax like built-in filters. Calling as a function or tag is invalid.

🔧 Debug

advanced

What error occurs with this filter usage in Flask template?

Consider this Flask template snippet:

{{ 123|lower }}

What error or output will this produce?

A AttributeError: 'int' object has no attribute 'lower'

B TypeError: 'int' object has no attribute 'lower'

C 123 (no change)

D 123

💡 Hint

The lower filter expects a string input.

The lower filter calls the string method lower(). Since 123 is an integer, it raises an AttributeError.

❓ state_output

advanced

What is the output of chaining filters in Flask template?

Given this template code:

{{ '  Flask Framework  ' | trim | upper }}

What will be the rendered output?

A Flask Framework

B KROWEMARF KSALF

C FLASK FRAMEWORK

D flask framework

💡 Hint

Filters are applied left to right. trim removes spaces, upper makes uppercase.

First, trim removes spaces around the string, then upper converts all letters to uppercase.

🧠 Conceptual

expert

Which statement about Flask template filters is TRUE?

Choose the correct statement about Flask template filters.

A Filters can be used to execute Python code directly inside templates.

B Custom filters must be registered with the Flask app before use in templates.

C Filters automatically modify variables in the Python code before rendering.

D Filters can only be applied to strings in templates.

💡 Hint

Think about how Flask connects custom filters to templates.

Custom filters must be registered with the Flask app to be available in templates. Filters do not modify Python variables directly and cannot execute arbitrary code.