Lambda with sorted() in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Sorting a list of tuples by second element using lambda

What is the output of this code?

data = [(3, 2), (1, 5), (4, 1)]
sorted_data = sorted(data, key=lambda x: x[1])
print(sorted_data)

Python

data = [(3, 2), (1, 5), (4, 1)]
sorted_data = sorted(data, key=lambda x: x[1])
print(sorted_data)

A [(1, 5), (3, 2), (4, 1)]

B [(4, 1), (3, 2), (1, 5)]

C [(3, 2), (4, 1), (1, 5)]

D [(4, 1), (1, 5), (3, 2)]

💡 Hint

Look at the second element of each tuple and how sorted() uses the lambda key.

The lambda function returns the second element of each tuple. sorted() arranges tuples by these values in ascending order.

❓ Predict Output

intermediate

Sorting strings by length using lambda

What is the output of this code?

words = ['apple', 'banana', 'fig', 'date']
sorted_words = sorted(words, key=lambda w: len(w))
print(sorted_words)

Python

words = ['apple', 'banana', 'fig', 'date']
sorted_words = sorted(words, key=lambda w: len(w))
print(sorted_words)

A ['fig', 'date', 'apple', 'banana']

B ['banana', 'apple', 'date', 'fig']

C ['apple', 'banana', 'date', 'fig']

D ['date', 'fig', 'apple', 'banana']

💡 Hint

Check the length of each word and how sorted() orders them.

The lambda returns the length of each word. sorted() orders words from shortest to longest.

❓ Predict Output

advanced

Sorting a list of dictionaries by nested key using lambda

What is the output of this code?

items = [{'name': 'apple', 'info': {'price': 5}}, {'name': 'banana', 'info': {'price': 3}}, {'name': 'cherry', 'info': {'price': 7}}]
sorted_items = sorted(items, key=lambda x: x['info']['price'])
print([item['name'] for item in sorted_items])

Python

items = [{'name': 'apple', 'info': {'price': 5}}, {'name': 'banana', 'info': {'price': 3}}, {'name': 'cherry', 'info': {'price': 7}}]
sorted_items = sorted(items, key=lambda x: x['info']['price'])
print([item['name'] for item in sorted_items])

A ['apple', 'banana', 'cherry']

B ['cherry', 'apple', 'banana']

C ['banana', 'apple', 'cherry']

D ['banana', 'cherry', 'apple']

💡 Hint

Look inside the nested dictionary to find the price for sorting.

The lambda accesses the nested 'price' key. sorted() orders items by price ascending.

❓ Predict Output

advanced

Sorting with lambda and reverse order

What is the output of this code?

numbers = [10, 3, 7, 1]
sorted_numbers = sorted(numbers, key=lambda x: -x)
print(sorted_numbers)

Python

numbers = [10, 3, 7, 1]
sorted_numbers = sorted(numbers, key=lambda x: -x)
print(sorted_numbers)

A [1, 3, 7, 10]

B [10, 3, 7, 1]

C ]01 ,7 ,3 ,1[

D [10, 7, 3, 1]

💡 Hint

The lambda negates each number, so sorting by negative values reverses order.

Sorting by negative values sorts numbers descending because bigger numbers have smaller negatives.

🧠 Conceptual

expert

Understanding lambda with sorted() behavior on complex keys

Given the code below, what is the output?

data = ['a1', 'a10', 'a2', 'a11']
sorted_data = sorted(data, key=lambda x: (x[0], int(x[1:])))
print(sorted_data)

Python

data = ['a1', 'a10', 'a2', 'a11']
sorted_data = sorted(data, key=lambda x: (x[0], int(x[1:])))
print(sorted_data)

A ['a1', 'a2', 'a10', 'a11']

B ['a1', 'a10', 'a11', 'a2']

C ['a10', 'a11', 'a1', 'a2']

D ['a11', 'a10', 'a2', 'a1']

💡 Hint

The lambda sorts first by the letter, then by the number part as integer.

The key is a tuple: first character 'a' (same for all), then integer from substring. So numbers sort numerically, not lexicographically.