HTTP methods (GET, POST, PUT, DELETE) in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Flask route that responds to GET requests.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/hello', methods=[[1]])
def hello():
    return 'Hello, world!'

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

A"PUT"

B"POST"

C"GET"

D"DELETE"

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST instead of GET for a route meant to retrieve data.

Forgetting to put the method name in quotes.

The methods parameter specifies which HTTP methods the route accepts. To respond to GET requests, use "GET".

2fill in blank

medium

Complete the code to handle POST requests in a Flask route.

Flask

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

@app.route('/submit', methods=[[1]])
def submit():
    data = request.form.get('data')
    return f'Received: {data}'

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

A"GET"

B"POST"

C"PUT"

D"DELETE"

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET instead of POST when expecting form data.

Not specifying the POST method in the route.

POST requests are used to send data to the server, so the route must accept "POST" to handle form data.

3fill in blank

hard

Fix the error in the Flask route to allow updating data with PUT method.

Flask

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

@app.route('/update', methods=[[1]])
def update():
    new_data = request.json.get('new_data')
    return f'Updated to: {new_data}'

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

A"PUT"

B"DELETE"

C"GET"

D"POST"

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST or GET instead of PUT for update operations.

Not including the PUT method in the route's methods list.

The PUT method is used to update existing data, so the route must accept "PUT" to handle update requests.

4fill in blank

hard

Fill in the blank to create a Flask route that deletes a resource using DELETE method and returns a confirmation message.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/delete-item', methods=[[1]])
def delete_item():
    # code to delete item
    return 'Item deleted!'

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

A"DELETE"

B"POST"

C"GET"

D"PUT"

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET or POST instead of DELETE for deletion.

Returning no confirmation message.

The DELETE method is used to remove resources, so the route must accept "DELETE". The return message can be any string; here, we use a simple confirmation message.

5fill in blank

hard

Fill all three blanks to create a Flask route that supports GET and POST methods and returns different messages based on the request method.

Flask

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

@app.route('/data', methods=[[1], [2]])
def data():
    if request.method == [3]:
        return 'This is a GET request'
    else:
        return 'This is a POST request'

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

A"GET"

B"POST"

D"PUT"

Attempts:

3 left

💡 Hint

Common Mistakes

Not including both GET and POST in the methods list.

Comparing request.method to the wrong string.

The route must accept both GET and POST methods. The request.method is compared to "GET" to decide the response.

Practice

1. Which HTTP method is typically used in Flask to retrieve data without changing anything on the server?

easy

A. PUT

B. POST

C. GET

D. DELETE

Solution

1. Step 1: Understand HTTP methods purpose

   GET is used to request data without modifying it, so it is safe and idempotent.

2. Step 2: Match method to Flask usage

   In Flask, GET routes are used to send data back to the client without changing server state.

3. Final Answer:

   GET -> Option C

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET reads data, POST creates, PUT updates, DELETE removes [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Using DELETE to get data
• Thinking PUT is for reading data

2. Which of the following Flask route definitions correctly allows handling both GET and POST methods?

easy

A. @app.route('/submit', allow_methods=['GET', 'POST'])

B. @app.route('/submit', methods=['GET', 'POST'])

C. @app.route('/submit', methods='GET, POST')

D. @app.route('/submit', method=['GET', 'POST'])

Solution

1. Step 1: Recall Flask route syntax for methods

   Flask uses the 'methods' keyword argument as a list of strings to specify allowed HTTP methods.

2. Step 2: Check each option's syntax

   @app.route('/submit', methods=['GET', 'POST']) correctly uses methods=['GET', 'POST']. Others have wrong keywords or wrong data types.

3. Final Answer:

   @app.route('/submit', methods=['GET', 'POST']) -> Option B

4. Quick Check:

   Correct keyword and list format = @app.route('/submit', methods=['GET', 'POST']) [OK]

Hint: Use methods=['GET', 'POST'] exactly in route decorator [OK]

Common Mistakes:

• Using 'method' instead of 'methods'
• Passing methods as a string instead of list
• Using unknown keywords like 'allow_methods'

3. What will be the output when a client sends a DELETE request to this Flask route?

@app.route('/item/', methods=['DELETE'])
def delete_item(id):
    return f"Deleted item {id}", 200

medium

A. "Deleted item <id>" with status 200

B. 404 Not Found error

C. Method Not Allowed error

D. Empty response with status 204

Solution

1. Step 1: Analyze route and method

   The route accepts DELETE requests with an integer id parameter and returns a string with status 200.

2. Step 2: Understand response for DELETE request

   Since the method matches and function returns a message with 200, the client receives that message and status.

3. Final Answer:

   "Deleted item <id>" with status 200 -> Option A

4. Quick Check:

   DELETE request handled correctly = "Deleted item <id>" with status 200 [OK]

Hint: Route method matches request method, so response is returned [OK]

Common Mistakes:

• Expecting 404 if route exists
• Confusing DELETE with GET behavior
• Assuming empty response without checking code

4. Identify the error in this Flask route that should handle PUT requests:

@app.route('/update', methods=['PUT'])
def update():
    data = request.get_json()
    return 'Updated', 200

medium

A. Missing import of 'request' from Flask

B. Incorrect HTTP method name 'PUT'

C. Route decorator syntax is invalid

D. Function must return JSON, not string

Solution

1. Step 1: Check usage of 'request'

   The function uses 'request.get_json()' but 'request' is not imported from Flask, causing a NameError.

2. Step 2: Verify other parts

   Method 'PUT' is valid, route syntax is correct, and returning string with status 200 is allowed.

3. Final Answer:

   Missing import of 'request' from Flask -> Option A

4. Quick Check:

   Using 'request' without import causes error [OK]

Hint: Always import 'request' to access request data [OK]

Common Mistakes:

• Forgetting to import 'request'
• Thinking PUT is invalid method
• Assuming string return is wrong

5. You want to create a Flask API endpoint to update a user's email using PUT and delete the user using DELETE at the same URL '/user/'. Which is the best way to define this in Flask?

hard

A. Use GET method for both update and delete actions

B. Create two separate routes with different URLs for PUT and DELETE

C. Use only POST method and check a hidden field for action

D. Use one route with methods=['PUT', 'DELETE'] and check request.method inside the function

Solution

1. Step 1: Understand RESTful design

   PUT and DELETE are standard methods for update and delete at the same resource URL.

2. Step 2: Implement in Flask

   Flask allows one route to handle multiple methods; inside the function, you check request.method to run correct code.

3. Final Answer:

   Use one route with methods=['PUT', 'DELETE'] and check request.method inside the function -> Option D

4. Quick Check:

   Multiple methods on one route with method check = Use one route with methods=['PUT', 'DELETE'] and check request.method inside the function [OK]

Hint: One route, multiple methods, check request.method inside [OK]

Common Mistakes:

• Creating separate URLs for same resource actions
• Using POST or GET incorrectly for update/delete
• Not checking request.method inside route