What is Flask - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Flask class from the flask package.

Flask

from flask import [1]

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

Arequest

Bflask

Capp

DFlask

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'flask' instead of 'Flask'.

Importing 'app' which is not a class.

Confusing 'request' with 'Flask'.

You need to import the Flask class to create a Flask app.

2fill in blank

medium

Complete the code to create a Flask app instance named 'app'.

Flask

app = [1](__name__)

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

AApp

BFlask

CApplication

DServer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Application' or 'App' which are not valid class names.

Using lowercase 'flask' which is incorrect here.

The Flask app instance is created by calling the Flask class with __name__ as argument.

3fill in blank

hard

Fix the error in the route decorator to define a route for the home page.

Flask

@app.route([1])
def home():
    return "Hello, Flask!"

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

A'/'

B'home'

C"/"

D"home"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'home' instead of '/' as the route path.

Using double quotes instead of single quotes is okay but here single quotes are expected.

Missing quotes around the path.

The route decorator needs the URL path as a string. The home page is '/'.

4fill in blank

hard

Fill both blanks to run the Flask app only when this script is executed directly.

Flask

if __name__ == [1]:
    app.run([2])

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

A"__main__"

BTrue

CFalse

Ddebug=True

Attempts:

3 left

💡 Hint

Common Mistakes

Using True or False instead of the string '__main__' in the if condition.

Not passing debug=True to app.run() for development.

The special variable __name__ equals "__main__" when the script runs directly. app.run(debug=True) starts the server with debug mode on.

5fill in blank

hard

Fill all three blanks to create a route '/about' that returns 'About page'.

Flask

@app.route([1])
def [2]():
    return [3]

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

A'/about'

Babout

C"About page"

D'About page'

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes for the return string is okay but here single quotes are expected.

Naming the function with capital letters or spaces.

Missing quotes around the route path.

The route decorator needs the path '/about'. The function name is about. The return value is the string 'About page'.

Practice

1. What is Flask primarily used for?

easy

A. Creating desktop applications

B. Building web applications with Python

C. Managing databases directly

D. Designing mobile apps

Solution

1. Step 1: Understand Flask's purpose

   Flask is a tool that helps developers create web applications using Python.

2. Step 2: Compare options with Flask's role

   Options A, C, and D describe other types of software development, not Flask's main use.

3. Final Answer:

   Building web applications with Python -> Option B

4. Quick Check:

   Flask = Web apps with Python [OK]

Hint: Flask = Python + web apps, not desktop or mobile [OK]

Common Mistakes:

• Thinking Flask is for desktop apps
• Confusing Flask with database tools
• Assuming Flask builds mobile apps

2. Which of the following is the correct way to start a basic Flask app?

easy

A. from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
return 'Hello, Flask!'

B. import flask
app = flask()

@app.route('/')
def home():
print('Hello, Flask!')

C. from flask import app
app = Flask()

@app.route('/')
def home():
return 'Hello, Flask!'

D. import Flask
app = Flask(__name__)

@app.route('/')
def home():
return 'Hello, Flask!'

Solution

1. Step 1: Check import and app creation

   from flask import Flask app = Flask(__name__) @app.route('/') def home(): return 'Hello, Flask!' correctly imports Flask and creates an app with Flask(__name__). Others have wrong imports or app creation.

2. Step 2: Verify route and return statement

   from flask import Flask app = Flask(__name__) @app.route('/') def home(): return 'Hello, Flask!' uses @app.route('/') and returns a string, which is correct Flask syntax.

3. Final Answer:

   Correct Flask app start code -> Option A

4. Quick Check:

   Correct import and route = from flask import Flask app = Flask(__name__) @app.route('/') def home(): return 'Hello, Flask!' [OK]

Hint: Import Flask and create app with Flask(__name__) [OK]

Common Mistakes:

• Using wrong import statements
• Calling flask() instead of Flask()
• Printing instead of returning response

3. What will this Flask route return when accessed?

from flask import Flask
app = Flask(__name__)

@app.route('/greet')
def greet():
    return 'Welcome to Flask!'

medium

A. Nothing, the route is not defined

B. A syntax error because of missing parentheses

C. A server error due to missing return statement

D. A web page showing 'Welcome to Flask!'

Solution

1. Step 1: Analyze the route definition

   The route '/greet' is defined with a function that returns the string 'Welcome to Flask!'.

2. Step 2: Understand Flask response behavior

   Flask sends the returned string as the response body, so visiting '/greet' shows that message.

3. Final Answer:

   A web page showing 'Welcome to Flask!' -> Option D

4. Quick Check:

   Route returns string response = A web page showing 'Welcome to Flask!' [OK]

Hint: Returned string is sent as web page content [OK]

Common Mistakes:

• Thinking return must be HTML tags
• Assuming missing parentheses cause error
• Believing route is undefined

4. Identify the error in this Flask app code:

from flask import Flask
app = Flask(__name__)

@app.route('/hello')
def hello():
    print('Hello World')

medium

A. Wrong app creation syntax

B. Incorrect import of Flask

C. Missing return statement in route function

D. Route decorator syntax error

Solution

1. Step 1: Check the route function body

   The function prints 'Hello World' but does not return anything, so Flask gets no response to send.

2. Step 2: Understand Flask route requirements

   Flask route functions must return a response string or object; printing does not send data to the client.

3. Final Answer:

   Missing return statement in route function -> Option C

4. Quick Check:

   Route must return response, not just print [OK]

Hint: Route functions must return, not print, response [OK]

Common Mistakes:

• Using print instead of return
• Assuming print sends response
• Ignoring missing return causes error

5. You want to create a Flask app that responds differently based on the URL path. Which feature helps you do this?

hard

A. Using multiple @app.route decorators with different paths

B. Using print statements inside one route

C. Creating multiple Flask app instances

D. Changing the Flask import statement

Solution

1. Step 1: Understand Flask routing

   Flask uses @app.route decorators to map different URL paths to different functions.

2. Step 2: Evaluate options for handling multiple paths

   Using multiple @app.route decorators with different paths allows different responses for each URL.

3. Final Answer:

   Using multiple @app.route decorators with different paths -> Option A

4. Quick Check:

   Multiple routes = different URL responses [OK]

Hint: Use multiple @app.route for different URLs [OK]

Common Mistakes:

• Thinking print changes URL response
• Creating multiple app instances unnecessarily
• Modifying import does not affect routing