Render_template function in Flask - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Flask route render?

Given this Flask route, what will the user see when visiting /hello?

Flask

from flask import Flask, render_template
app = Flask(__name__)

@app.route('/hello')
def hello():
    return render_template('greet.html', name='Alice')

A The content of greet.html with the variable 'name' replaced by 'Alice'.

B A plain text response saying 'Hello Alice'.

C An error because 'name' is not defined in the template.

D A JSON response with {'name': 'Alice'}.

💡 Hint

Think about what render_template does with the variables passed to it.

render_template loads the HTML file and replaces placeholders with the variables given, so the user sees the HTML with 'Alice' where 'name' is used.

📝 Syntax

intermediate

Identify the syntax error in this render_template usage

What is wrong with this Flask route code?

Flask

from flask import Flask, render_template
app = Flask(__name__)

@app.route('/user')
def user():
    return render_template('user.html', username=)

A render_template cannot be used inside a route function.

B Missing value for 'username' keyword argument in render_template.

C The template file 'user.html' must be a Python file.

D Flask app must be run with debug=True to use render_template.

💡 Hint

Check how variables are passed to render_template.

render_template expects keyword arguments like 'username=value'. Here, 'username' is passed without a value, causing a syntax error.

❓ state_output

advanced

What is the output of this Flask route with conditional rendering?

Consider this route and template. What will the user see when visiting /status?

Flask

from flask import Flask, render_template
app = Flask(__name__)

@app.route('/status')
def status():
    user_logged_in = False
    return render_template('status.html', logged_in=user_logged_in)

# status.html content:
# {% if logged_in %}
# <p>Welcome back!</p>
# {% else %}
# <p>Please log in.</p>
# {% endif %}

A <p>Please log in.</p>

B An empty page with no content.

C An error because 'logged_in' is not a boolean.

D <p>Welcome back!</p>

💡 Hint

Look at the value of 'user_logged_in' and the template's if condition.

The variable 'logged_in' is False, so the else block runs, showing 'Please log in.'

🔧 Debug

advanced

Why does this Flask app raise a TemplateNotFound error?

This Flask route raises a TemplateNotFound error. What is the most likely cause?

Flask

from flask import Flask, render_template
app = Flask(__name__)

@app.route('/page')
def page():
    return render_template('mypage.html')

A The route function must return a string, not render_template.

B Flask app must be run with debug=True to find templates.

C The template file 'mypage.html' is missing from the 'templates' folder.

D render_template requires the template file to be in the static folder.

💡 Hint

Check where Flask looks for template files by default.

Flask looks for templates in the 'templates' folder. If 'mypage.html' is missing there, TemplateNotFound error occurs.

🧠 Conceptual

expert

How does Flask's render_template handle variable scope?

When you pass variables to render_template, how are they accessed inside the template?

A Variables are only accessible inside Python code blocks, not in HTML parts.

B Variables must be declared global in the template to be accessed.

C Variables passed are converted to JSON strings and must be parsed in the template.

D Variables passed as keyword arguments become available as template variables with the same names.

💡 Hint

Think about how templates use placeholders for variables.

Flask injects the passed variables into the template context, so you can use them directly by name in the template.