Route with dynamic parameters in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a route that accepts a dynamic username parameter.

Flask

from flask import Flask
app = Flask(__name__)

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

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

A(username)

B<username>

C[username]

D{username}

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets or parentheses instead of angle brackets.

In Flask, dynamic route parameters are enclosed in <> brackets.

2fill in blank

medium

Complete the code to convert the dynamic parameter to an integer in the route.

Flask

@app.route('/post/[1]')
def show_post(post_id):
    return f"Post ID: {post_id}"

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

A<int:post_id>

B<str:post_id>

C<post_id>

D<float:post_id>

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the type converter or using the wrong type.

Use <int:parameter> to convert the route parameter to an integer.

3fill in blank

hard

Fix the error in the route decorator to correctly capture a float parameter named price.

Flask

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

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

A<float:price>

B<int:price>

C<price>

D<str:price>

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or str instead of float for decimal values.

Use <float:price> to capture a floating-point number in the route.

4fill in blank

hard

Fill both blanks to create a route that accepts a string category and an integer item_id.

Flask

@app.route('/shop/[1]/[2]')
def show_item(category, item_id):
    return f"Category: {category}, Item ID: {item_id}"

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

A<string:category>

B<int:item_id>

C<category>

D<item_id>

Attempts:

3 left

💡 Hint

Common Mistakes

Not specifying types or mixing up parameter names.

Use <string:category> and <int:item_id> to specify types for both parameters.

5fill in blank

hard

Fill all three blanks to define a route with a string username, an integer year, and a float rating.

Flask

@app.route('/profile/[1]/[2]/[3]')
def profile(username, year, rating):
    return f"User: {username}, Year: {year}, Rating: {rating}"

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

A<string:username>

B<int:year>

C<float:rating>

D<user>

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect types or missing type converters.

Use <string:username>, <int:year>, and <float:rating> to define the route parameters with types.

Practice

1. What does the dynamic parameter in a Flask route do?
@app.route('/user/<username>')

easy

A. It captures the part of the URL as a variable passed to the function.

B. It creates a fixed URL that never changes.

C. It makes the route only accept numbers.

D. It disables the route from working.

Solution

1. Step 1: Understand dynamic parameters in Flask routes

   Dynamic parameters are parts of the URL wrapped in <> that Flask captures as variables.

2. Step 2: How Flask uses the captured variable

   The captured part is passed as an argument to the view function to use inside the code.

3. Final Answer:

   It captures the part of the URL as a variable passed to the function. -> Option A

4. Quick Check:

   Dynamic parameter = variable in function [OK]

Hint: Dynamic parts in <> become function arguments [OK]

Common Mistakes:

• Thinking dynamic means fixed URL
• Assuming only numbers can be captured
• Believing dynamic disables the route

2. Which of these is the correct syntax to define a route with an integer parameter named post_id?

easy

A. @app.route('/post/')

B. @app.route('/post/<post_id>')

C. @app.route('/post/')

D. @app.route('/post/')

Solution

1. Step 1: Identify the type syntax for dynamic parameters

   Flask uses <type:name> to specify the parameter type, like int for integers.

2. Step 2: Match the correct syntax for integer parameter

   The correct syntax is <int:post_id> to ensure only integers are accepted.

3. Final Answer:

   @app.route('/post/<int:post_id>') -> Option A

4. Quick Check:

   Integer type uses <int:name> [OK]

Hint: Use <int:name> for integer parameters in routes [OK]

Common Mistakes:

• Omitting the type for integer parameters
• Using str instead of int for numbers
• Using float when integer is needed

3. What will be the output if you visit /product/42 given this Flask route?

@app.route('/product/')
def product(id):
    return f"Product ID: {id}"

medium

A. 404 Not Found error

B. Product ID:

C. Product ID: id

D. Product ID: 42

Solution

1. Step 1: Understand the route and parameter type

   The route expects an integer parameter named id, which matches 42 in the URL.

2. Step 2: Check the function return value

   The function returns a string with the id value inserted, so it returns "Product ID: 42".

3. Final Answer:

   Product ID: 42 -> Option D

4. Quick Check:

   Dynamic int parameter outputs value [OK]

Hint: Dynamic int parameter passes number as function argument [OK]

Common Mistakes:

• Expecting the literal string instead of value
• Confusing parameter name with string
• Assuming route returns error for valid int

4. Identify the error in this Flask route definition:

@app.route('/item/')
def item(item):
    return f"Item {item_id}"

medium

A. Route parameter type int is invalid.

B. Function parameter name does not match route parameter name.

C. Missing return statement in function.

D. Route URL should not have dynamic parameters.

Solution

1. Step 1: Compare route parameter and function argument names

   The route defines <int:item_id> but the function uses parameter named item, which is inconsistent.

2. Step 2: Understand how Flask matches parameters

   Flask passes the URL part as argument named item_id, so function must accept item_id to receive it correctly.

3. Final Answer:

   Function parameter name does not match route parameter name. -> Option B

4. Quick Check:

   Parameter names must match [OK]

Hint: Function argument must match route parameter name exactly [OK]

Common Mistakes:

• Using different names for route and function parameters
• Thinking type int is invalid syntax
• Forgetting to return a value

5. You want a Flask route that accepts a username (string) and an optional integer page number with default 1. Which route and function definition is correct?

hard

A. @app.route('/profile/<username>/')
def profile(username, page=1):
return f"User: {username}, Page: {page}"

B. @app.route('/profile/<username>/<page>')
def profile(username, page=1):
return f"User: {username}, Page: {page}"

C. @app.route('/profile/<username>')
def profile(username, page=1):
return f"User: {username}, Page: {page}"

D. @app.route('/profile/<username>/')
def profile(username, page):
return f"User: {username}, Page: {page}"

Solution

1. Step 1: Understand optional parameters in Flask routes

   Flask routes do not support optional URL parts directly; optional parameters must be handled with defaults in function and route without that part.

2. Step 2: Check which route allows optional page parameter

   Route with only <username> works, and function uses default page=1 if not provided.

3. Final Answer:

   @app.route('/profile/<username>')\ndef profile(username, page=1):\n return f"User: {username}, Page: {page}" -> Option C

4. Quick Check:

   Optional params handled by function defaults, not route [OK]

Hint: Optional URL parts need separate routes or defaults in function [OK]

Common Mistakes:

• Assuming Flask supports optional URL parts in one route
• Using default values with required route parameters
• Mismatching parameter types in route and function