Hackerrank - HackerRank Python Built-in Functions and Lambdas Questions and Answers

Question 1

A list of dictionaries needs to be sorted based on the 'age' of each person. Which of the following code snippets correctly performs this sort?

Accepted Answer

sorted(people, key=lambda person: person['age'])

Answer

people.sort(lambda person: person['age'])

Answer

sorted(people, 'age')

Answer

people.sort(key='age')

Question 2

What is the primary characteristic that distinguishes a lambda function from a standard function defined with `def`?

Accepted Answer

A lambda function is restricted to a single expression and implicitly returns its result.

Answer

A lambda function can be used as an argument to other functions, while a `def` function cannot.

Answer

A lambda function can have default argument values, but a `def` function cannot.

Answer

A lambda function must be assigned to a variable, whereas a `def` function is automatically named.

Question 3

Given a list of integers, `numbers = [10, 15, 21, 33, 42, 55]`, which line of code will produce a new list containing only the numbers divisible by 5?

Accepted Answer

list(filter(lambda x: x % 5 == 0, numbers))

Answer

list(map(lambda x: x % 5 == 0, numbers))

Answer

filter(lambda x: x / 5, numbers)

Answer

map(lambda x: x, numbers, key=lambda x: x % 5 == 0)

Question 4

What will be the output of the following Python code snippet?

```python
from functools import reduce

items =
result = reduce(lambda x, y: x * y, items)
print(result)
```

Accepted Answer

24

Answer

[1, 2, 6, 24]

Answer

10

Answer

A TypeError because reduce is not a built-in function.

Question 5

A developer needs to create a new list where each number from an original list is tripled. Which of the following is the most idiomatic use of a built-in function with a lambda to achieve this?

Accepted Answer

list(map(lambda x: x * 3, original_list))

Answer

list(filter(lambda x: x * 3, original_list))

Answer

reduce(lambda x: x * 3, original_list)

Answer

[x * 3 for x in original_list using lambda]

Question 6

In which scenario is using a lambda function most appropriate over a standard named function (`def`)?

Accepted Answer

When a simple, one-off function is needed as an argument for a higher-order function like `sorted()` or `map()`.

Answer

When a complex, multi-line function needs to be passed as an argument to a higher-order function.

Answer

When a function needs to be reused in multiple parts of the program.

Answer

When a function requires type hints and a docstring for clarity.