Accessing query parameters in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get the value of the 'name' query parameter in a Flask route.

Flask

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

@app.route('/hello')
def hello():
    name = request.args.get([1])
    return f"Hello, {name}!"

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

A'query'

B'user'

C'id'

D'name'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong key string inside get(), like 'user' or 'id'.

Forgetting to use quotes around the key.

The query parameter key is 'name', so request.args.get('name') retrieves its value.

2fill in blank

medium

Complete the code to provide a default value 'Guest' if the 'name' query parameter is missing.

Flask

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

@app.route('/welcome')
def welcome():
    name = request.args.get('name', [1])
    return f"Welcome, {name}!"

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

ANone

B''

C'Guest'

D'User'

Attempts:

3 left

💡 Hint

Common Mistakes

Using None which returns None instead of a string.

Forgetting quotes around the default string.

The second argument to get() is the default value returned if the parameter is missing. 'Guest' is the desired default.

3fill in blank

hard

Fix the error in the code to correctly access the 'age' query parameter as an integer.

Flask

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

@app.route('/age')
def age():
    age = int(request.args.get([1], 0))
    return f"Age is {age}"

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

A'age'

Bage

C'Age'

D'AGE'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name without quotes.

Using wrong case like 'Age' or 'AGE'.

The key must be the exact string 'age' matching the query parameter name. Using a variable or wrong case causes errors.

4fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps each query parameter key to its value.

Flask

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

@app.route('/params')
def params():
    params_dict = { [1]: [2] for [3] in request.args }
    return str(params_dict)

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

Akey

Bvalue

Crequest.args[key]

Dfor

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'value' as loop variable instead of 'key'.

Forgetting to use request.args[key] to get the value.

In a dictionary comprehension, the syntax is {key: value for key in iterable}. Here, key is 'key', value is request.args[key], and the loop variable is 'key'.

5fill in blank

hard

Fill all three blanks to filter query parameters with values longer than 3 characters into a new dictionary.

Flask

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

@app.route('/filter')
def filter_params():
    filtered = { [1]: [2] for [3] in request.args if len(request.args[[3]]) > 3 }
    return str(filtered)

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

Akey

Brequest.args[key]

Cvalue

Drequest.args

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'value' as loop variable but not defining it.

Not accessing the value correctly with request.args[key].

The dictionary comprehension uses 'key' as the loop variable, maps key to request.args[key], and filters by length of the value.

Practice

1. In Flask, which method is used to safely access a query parameter named user from the URL?

easy

A. request.form['user']

B. request.args.get('user')

C. request.query['user']

D. request.params.get('user')

Solution

1. Step 1: Understand Flask request object

   Flask's request object holds incoming request data, including query parameters in args.

2. Step 2: Use the correct method to access query parameters

   request.args.get('user') safely retrieves the value of the user parameter or returns None if missing.

3. Final Answer:

   request.args.get('user') -> Option B

4. Quick Check:

   Use args.get() for query parameters [OK]

Hint: Use request.args.get('param') to read query parameters [OK]

Common Mistakes:

• Using request.form for query parameters
• Trying to access request.query which doesn't exist
• Using request.params instead of request.args

2. Which of the following is the correct syntax to get a query parameter page with a default value of 1 in Flask?

easy

A. request.args.get('page', default=1)

B. request.args.get('page', 1)

C. request.args['page'] or 1

D. request.args.get('page', fallback=1)

Solution

1. Step 1: Check the get() method parameters

   The get() method accepts a default keyword argument to provide a fallback value if the parameter is missing.

2. Step 2: Identify correct syntax for default

   Using request.args.get('page', default=1) correctly sets 1 as default. Passing 1 as second positional argument is invalid.

3. Final Answer:

   request.args.get('page', default=1) -> Option A

4. Quick Check:

   Use default= for fallback in get() [OK]

Hint: Use default= in get() to set fallback value [OK]

Common Mistakes:

• Passing default value as second positional argument
• Using fallback= which is not valid in Flask
• Accessing with [] which raises error if missing

3. What will be the output of this Flask route when accessed with URL /search?term=flask?

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

@app.route('/search')
def search():
    term = request.args.get('term', 'none')
    return f"Search term: {term}"

medium

A. Error: term parameter missing

B. Search term: none

C. Search term:

D. Search term: flask

Solution

1. Step 1: Understand the URL query parameter

   The URL contains ?term=flask, so the query parameter term has value 'flask'.

2. Step 2: Check how term is retrieved in code

   request.args.get('term', 'none') returns 'flask' because the parameter exists.

3. Final Answer:

   Search term: flask -> Option D

4. Quick Check:

   Parameter present returns its value, not default [OK]

Hint: If parameter exists, get() returns its value, else default [OK]

Common Mistakes:

• Assuming default is returned even if parameter exists
• Confusing query parameters with form data
• Expecting empty string instead of actual value

4. Identify the error in this Flask code snippet that tries to get a query parameter id:

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

@app.route('/item')
def item():
    id = request.args['id']
    return f"Item ID: {id}"

medium

A. Using request.args['id'] raises KeyError if 'id' missing

B. Missing import of request module

C. Route decorator syntax is incorrect

D. Using f-string inside return is invalid

Solution

1. Step 1: Analyze how query parameter is accessed

   Using request.args['id'] accesses the parameter directly and raises KeyError if missing.

2. Step 2: Identify safer alternative

   Using request.args.get('id') avoids error by returning None if missing.

3. Final Answer:

   Using request.args['id'] raises KeyError if 'id' missing -> Option A

4. Quick Check:

   Direct dict access can cause KeyError [OK]

Hint: Use get() to avoid KeyError when parameter might be missing [OK]

Common Mistakes:

• Assuming request.args['id'] never fails
• Ignoring possibility of missing parameters
• Confusing import errors with runtime errors

5. You want to create a Flask route /filter that reads two optional query parameters: category (default 'all') and limit (default 10, integer). Which code correctly handles both parameters safely?

hard

A. category = request.args.get('category') or 'all'
limit = int(request.args.get('limit', 10))

B. category = request.args['category'] or 'all'
limit = int(request.args['limit'] or 10)

C. category = request.args.get('category', default='all')
limit = int(request.args.get('limit', default=10))

D. category = request.args.get('category', 'all')
limit = int(request.args.get('limit', '10'))

Solution

1. Step 1: Handle category parameter with default

   Using request.args.get('category', default='all') safely returns 'all' if missing.

2. Step 2: Handle limit parameter with default and convert to int

   request.args.get('limit', default=10) returns string or int 10; wrapping with int() converts string to integer safely.

3. Step 3: Check other options for errors

   category = request.args['category'] or 'all' limit = int(request.args['limit'] or 10) risks KeyError; category = request.args.get('category') or 'all' limit = int(request.args.get('limit', 10)) uses positional default incorrectly; category = request.args.get('category', 'all') limit = int(request.args.get('limit', '10')) converts default string '10' which works but less clear than int 10.

4. Final Answer:

   category = request.args.get('category', default='all')\nlimit = int(request.args.get('limit', default=10)) -> Option C

5. Quick Check:

   Use get() with default and convert types explicitly [OK]

Hint: Use get() with default and convert types explicitly [OK]

Common Mistakes:

• Using [] which raises error if missing
• Passing default as positional argument incorrectly
• Not converting string query param to int