Hackerrank Decorators and Closures

Question 1

What is a closure in Python?

Accepted Answer

A function that retains access to variables from its enclosing scope even after that scope has finished executing

Answer

A function defined inside a class

Answer

A function that cannot be called from outside its module

Answer

A function with no return statement

Question 2

What does the following code print?

python
def make_multiplier(n):
    def multiply(x):
        return x * n
    return multiply

double = make_multiplier(2)
print(double(5))

Accepted Answer

10

Answer

2

Answer

5

Answer

Error: n is not defined

Question 3

What is the effect of applying a decorator using @syntax?

python
@my_decorator
def greet():
    return 'hello'

Accepted Answer

It is equivalent to greet = my_decorator(greet)

Answer

It calls my_decorator() and then calls greet()

Answer

It makes greet a method of my_decorator

Answer

It applies my_decorator only when greet raises an exception

Question 4

Why is functools.wraps used inside a decorator?

Accepted Answer

To preserve the original function's __name__ and __doc__ on the wrapper function

Answer

To make the decorator work with class methods

Answer

To prevent the decorator from being applied more than once

Answer

To ensure the wrapper function runs in a separate thread

Question 5

What does the nonlocal keyword do in the following code?

python
def counter():
    count = 0
    def increment():
        nonlocal count
        count += 1
        return count
    return increment

Accepted Answer

Allows increment() to modify the count variable in counter()'s scope

Answer

Makes count a global variable

Answer

Creates a new local variable count inside increment()

Answer

Raises a SyntaxError because count is already defined

Question 6

What is the output of the following decorator example?

python
def shout(func):
    def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        return result.upper()
    return wrapper

@shout
def greet(name):
    return f'hello {name}'

print(greet('world'))

Accepted Answer

HELLO WORLD

Answer

hello world

Answer

Hello World

Answer

hello WORLD