Parameter type converters (int, float, path) in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a route that accepts an integer parameter named <user_id>.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/user/[1]')
def show_user(user_id):
    return f"User ID is {user_id}"

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

A<int:user_id>

B<string:user_id>

C<float:user_id>

D<path:user_id>

Attempts:

3 left

💡 Hint

Common Mistakes

Using will treat the parameter as text, not an integer.

Forgetting the converter and just using treats it as a string.

Using tells Flask to convert the URL part to an integer before passing it to the function.

2fill in blank

medium

Complete the code to define a route that accepts a floating-point number parameter named <price>.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/price/[1]')
def show_price(price):
    return f"Price is {price}"

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

A<path:price>

B<int:price>

C<float:price>

D<string:price>

Attempts:

3 left

💡 Hint

Common Mistakes

Using will cause errors if the URL has decimals.

Using treats the parameter as text.

The <float:price> converter converts the URL part to a floating-point number.

3fill in blank

hard

Fix the error in the route to accept a file path parameter named <filepath> that can include slashes.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/files/[1]')
def show_file(filepath):
    return f"File path is {filepath}"

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

A<path:filepath>

B<int:filepath>

C<string:filepath>

D<float:filepath>

Attempts:

3 left

💡 Hint

Common Mistakes

Using stops at the first slash, so the path is incomplete.

Using or causes type errors.

The <path:filepath> converter allows slashes in the parameter, capturing the full path.

4fill in blank

hard

Fill both blanks to create a route that accepts an integer <post_id> and a path <filename>.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/post/[1]/file/[2]')
def show_post_file(post_id, filename):
    return f"Post {post_id}, File {filename}"

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

A<int:post_id>

B<string:filename>

C<path:filename>

D<float:post_id>

Attempts:

3 left

💡 Hint

Common Mistakes

Using will not capture slashes in the filename.

Using is incorrect if the ID is an integer.

The first blank uses <int:post_id> to get an integer post ID. The second uses <path:filename> to accept a file path with slashes.

5fill in blank

hard

Fill all three blanks to create a route that accepts a float <rating>, an int <item_id>, and a path <image_path>.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/rate/[1]/item/[2]/image/[3]')
def show_rating(rating, item_id, image_path):
    return f"Rating: {rating}, Item: {item_id}, Image: {image_path}"

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

A<string:image_path>

B<int:item_id>

C<path:image_path>

D<float:rating>

Attempts:

3 left

💡 Hint

Common Mistakes

Using will not capture slashes.

Mixing up the order of converters causes errors.

The route uses <float:rating> for decimal ratings, <int:item_id> for integer item IDs, and <path:image_path> to accept image paths with slashes.

Practice

1. What does the int converter do in a Flask route parameter like <int:id>?

easy

A. It matches any text including slashes.

B. It ensures the parameter is an integer and converts it automatically.

C. It converts the parameter to a string.

D. It converts the parameter to a floating-point number.

Solution

1. Step 1: Understand the role of int converter

   The int converter tells Flask to accept only integer values for that URL part.

2. Step 2: Check what happens with the parameter

   Flask automatically converts the matched URL part to an integer type before passing it to the view function.

3. Final Answer:

   It ensures the parameter is an integer and converts it automatically. -> Option B

4. Quick Check:

   int converter = integer parameter [OK]

Hint: int converter means only whole numbers allowed [OK]

Common Mistakes:

• Thinking int converts to string
• Confusing int with float converter
• Assuming int matches any text

2. Which of the following is the correct syntax to define a Flask route that accepts a floating-point number parameter named price?

easy

A. @app.route('/item/<path:price>')

B. @app.route('/item/<int:price>')

C. @app.route('/item/<float:price>')

D. @app.route('/item/<str:price>')

Solution

1. Step 1: Identify the correct converter for floating-point numbers

   The float converter is used to accept decimal numbers in the URL.

2. Step 2: Match the syntax for route parameter

   The correct syntax is <float:price> inside the route decorator.

3. Final Answer:

   @app.route('/item/<float:price>') -> Option C

4. Quick Check:

   float converter = decimal number parameter [OK]

Hint: Use for decimal numbers in route parameters [OK]

Common Mistakes:

• Using int instead of float for decimals
• Using str which is not a Flask converter
• Using path which allows slashes, not numbers

3. Given this Flask route:

@app.route('/files/<path:filename>')
def show_file(filename):
    return f"File requested: {filename}"

What will be the output if the URL is /files/docs/manual.pdf?

medium

A. File requested: docs/manual.pdf

B. File requested: manual.pdf

C. 404 Not Found error

D. File requested: docs

Solution

1. Step 1: Understand the path converter behavior

   The path converter matches the entire remaining path including slashes.

2. Step 2: Analyze the URL and parameter value

   The URL /files/docs/manual.pdf matches filename as docs/manual.pdf.

3. Final Answer:

   File requested: docs/manual.pdf -> Option A

4. Quick Check:

   path converter = matches full path with slashes [OK]

Hint: path converter captures slashes in URL parts [OK]

Common Mistakes:

• Assuming path stops at first slash
• Expecting 404 error for slashes in parameter
• Confusing path with string converter

4. What is wrong with this Flask route definition?

@app.route('/product/<int:product_id>/<float:price>')
def show_product(product_id, price):
    return f"Product {product_id} costs {price}"

When accessing /product/abc/19.99, what error occurs?

medium

A. ValueError because 'abc' is not an integer

B. TypeError because price is not a float

C. No error, it works fine

D. 404 Not Found error due to URL mismatch

Solution

1. Step 1: Check the int converter requirement

   The first parameter expects an integer, but 'abc' is not an integer.

2. Step 2: Understand Flask routing behavior on type mismatch

   Flask does not raise ValueError but returns 404 Not Found if the URL does not match the route pattern.

3. Final Answer:

   404 Not Found error due to URL mismatch -> Option D

4. Quick Check:

   Type mismatch in route = 404 error [OK]

Hint: Wrong type in URL parameter causes 404, not exception [OK]

Common Mistakes:

• Expecting Python exceptions instead of 404
• Confusing ValueError with Flask routing errors
• Assuming route matches any string

5. You want to create a Flask route that accepts a file path parameter which may include slashes, and an integer version number after it, like /download/docs/manual/2. Which route definition correctly uses converters to achieve this?

hard

A. @app.route('/download/<path:filepath>/<int:version>')

B. @app.route('/download/<int:version>/<path:filepath>')

C. @app.route('/download/<path:filepath><int:version>')

D. @app.route('/download/<path:filepath>/<float:version>')

Solution

1. Step 1: Identify the order of parameters in the URL

   The URL pattern is /download/ followed by a path (which may include slashes), then a slash, then an integer version.

2. Step 2: Use path for filepath and int for version in correct order

   The route must be /download/<path:filepath>/<int:version> to match the URL structure.

3. Final Answer:

   @app.route('/download/<path:filepath>/<int:version>') -> Option A

4. Quick Check:

   path then int in route matches URL structure [OK]

Hint: Use path converter before int for multi-part paths [OK]

Common Mistakes:

• Swapping parameter order
• Missing slash between parameters
• Using float instead of int for version