Macros for reusable components in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a macro named 'button' in a Jinja2 template.

Flask

{% macro [1](text) %}
  <button>{{ text }}</button>
{% endmacro %}

Drag options to blanks, or click blank then click option'

Abtn

Bmacro

Cbutton

Dcomponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'macro' as the macro name instead of the actual component name.

Using a generic name like 'component' which is not descriptive.

The macro is named 'button' to define a reusable button component.

2fill in blank

medium

Complete the code to call the macro 'button' with the label 'Click me'.

Flask

{{ [1]('Click me') }}

Drag options to blanks, or click blank then click option'

Acall_button

Bmacro

Cbtn

Dbutton

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'call_button' which is not defined.

Using 'macro' which is a keyword, not the macro name.

To use the macro named 'button', call it by its name with the argument.

3fill in blank

hard

Fix the error in the macro call to pass the variable 'label' as the button text.

Flask

{{ button([1]) }}

Drag options to blanks, or click blank then click option'

Alabel

B'label'

Cbutton

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Passing 'label' as a string instead of a variable.

Passing unrelated names like 'text' or 'button'.

Pass the variable 'label' without quotes to use its value in the macro.

4fill in blank

hard

Fill both blanks to import the macro file and use the macro 'button' from it.

Flask

{% import '[1]' as [2] %}
{{ [2].button('Submit') }}

Drag options to blanks, or click blank then click option'

Amacros.html

Bcomponents.html

Cbtns.html

Dbuttons.html

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong file names that don't exist.

Using alias names that are not used in the macro call.

Import the macro file 'macros.html' and assign it an alias 'components' to use its macros.

5fill in blank

hard

Fill all three blanks to define a macro with a default argument and call it with a custom label.

Flask

{% macro [1](text='[2]') %}
  <button>{{ text }}</button>
{% endmacro %}

{{ [3]('Save') }}

Drag options to blanks, or click blank then click option'

Abutton

BClick me

CSubmit

Dbtn

Attempts:

3 left

💡 Hint

Common Mistakes

Using different macro names in definition and call.

Not quoting the default argument string.

Define macro 'button' with default text 'Click me' and call it with 'Save' label.

Practice

1. What is the main purpose of using {% macro %} in Flask templates?

easy

A. To create reusable blocks of HTML code

B. To define Python functions inside templates

C. To import external CSS files

D. To handle form submissions

Solution

1. Step 1: Understand what macros do in Flask templates

   Macros are used to write reusable HTML blocks that can be called multiple times to avoid repetition.

2. Step 2: Compare options with macro purpose

   Only To create reusable blocks of HTML code correctly describes macros as reusable HTML blocks. Other options describe unrelated tasks.

3. Final Answer:

   To create reusable blocks of HTML code -> Option A

4. Quick Check:

   Macros = reusable HTML blocks [OK]

Hint: Macros create reusable HTML snippets in templates [OK]

Common Mistakes:

• Thinking macros define Python functions
• Confusing macros with CSS imports
• Assuming macros handle form data

2. Which of the following is the correct syntax to define a macro named button that takes a parameter label?

easy

A. {% define button(label) %} {{ label }} {% enddefine %}

B. {% macro button(label) %} {{ label }} {% endmacro %}

C. {{ macro button(label) }} {{ label }} {{ endmacro }}

D. <% macro button(label) %> {{ label }} <% endmacro %>

Solution

1. Step 1: Recall correct macro syntax in Flask Jinja templates

   Macros are defined with {% macro name(params) %} ... {% endmacro %} tags.

2. Step 2: Check each option's syntax

   {% macro button(label) %} {{ label }} {% endmacro %} uses correct {% %} tags and endmacro. Others use wrong delimiters or keywords.

3. Final Answer:

   {% macro button(label) %} <button>{{ label }}</button> {% endmacro %} -> Option B

4. Quick Check:

   Macro syntax = {% macro %} ... {% endmacro %} [OK]

Hint: Use {% macro %} and {% endmacro %} to define macros [OK]

Common Mistakes:

• Using {{ }} instead of {% %} for macro definition
• Using incorrect keywords like define or <% %>
• Forgetting the endmacro tag

3. Given the macro defined in macros.html as:

{% raw %}{% macro greet(name) %}Hello, {{ name }}!{% endmacro %}{% endraw %}

And imported in index.html with:

{% raw %}{% import 'macros.html' as m %}{% endraw %}

What will be the output of {{ m.greet('Alice') }} in index.html?

medium

A. Error: macro not found

B. {{ m.greet('Alice') }}

C. greet('Alice')

D. Hello, Alice!

Solution

1. Step 1: Understand macro import and usage

   The macro greet(name) returns 'Hello, {{ name }}!'. Importing as m allows calling m.greet('Alice').

2. Step 2: Evaluate the macro call output

   Calling m.greet('Alice') replaces {{ name }} with 'Alice', so output is 'Hello, Alice!'.

3. Final Answer:

   Hello, Alice! -> Option D

4. Quick Check:

   Macro call with parameter = rendered string [OK]

Hint: Imported macros called with alias render output [OK]

Common Mistakes:

• Expecting literal macro call text instead of rendered output
• Forgetting to import macros before use
• Confusing macro call syntax with variable output

4. What is wrong with this macro usage in a Flask template?

{% raw %}{% macro card(title) %}
{{ title }}
{% endmacro %}{% endraw %}
{{ card() }}

medium

A. The macro is not properly closed with {% endmacro %}

B. Macros cannot return HTML elements

C. The macro is called without the required parameter

D. The macro name is invalid

Solution

1. Step 1: Check macro definition and parameters

   The macro card requires one parameter: title.

2. Step 2: Check macro call

   The call {{ card() }} provides no argument, causing an error due to missing parameter.

3. Final Answer:

   The macro is called without the required parameter -> Option C

4. Quick Check:

   Missing macro argument = error [OK]

Hint: Always pass required parameters when calling macros [OK]

Common Mistakes:

• Calling macros without required arguments
• Thinking macros must return plain text only
• Missing endmacro tag (not the case here)

5. You want to create a reusable navigation bar macro that highlights the current page. Which approach correctly uses macros and parameters to achieve this?

hard

A. {% raw %}{% macro navbar(current) %}HomeAbout{% endmacro %}{% endraw %} Then call with {{ navbar('about') }}

B. {% raw %}{% macro navbar() %}HomeAbout{% endmacro %}{% endraw %} Then call with {{ navbar() }}

C. {% raw %}{% macro navbar(current) %}HomeAbout{% endmacro %}{% endraw %} Then call with {{ navbar('home') }}

D. {% raw %}{% macro navbar(current) %}HomeAbout{% endmacro %}{% endraw %} Then call with {{ navbar('home') }}

Solution

1. Step 1: Understand the need for dynamic class assignment

   The macro should accept a parameter to know which page is current and add 'active' class accordingly.

2. Step 2: Analyze each option's approach

   {% raw %}{% macro navbar(current) %}
   HomeAbout
   {% endmacro %}{% endraw %} Then call with {{ navbar('about') }} uses a parameter and conditional expression to add 'active' class only to the current page link. Others either hardcode classes or ignore the parameter.

3. Final Answer:

   Uses parameters and conditional logic to highlight current page -> Option A

4. Quick Check:

   Dynamic class with parameter = correct navbar macro [OK]

Hint: Use macro parameters with conditionals for dynamic HTML [OK]

Common Mistakes:

• Hardcoding active class without parameters
• Ignoring the current page parameter
• Assigning 'current' class to all links