PCAP Closures and Decorators

Question 1

What is a closure in Python?

Accepted Answer

An inner function that captures and remembers variables from the enclosing scope even after the outer function has returned

Answer

A function that returns multiple values using a tuple

Answer

A class that implements the __call__ method to behave like a function

Answer

A function that blocks access to global variables

Question 2

What will the following code print?

def outer(x):
    def inner(y):
        return x + y
    return inner

add5 = outer(5)
print(add5(3))

Accepted Answer

8

Answer

5

Answer

3

Answer

TypeError: unsupported operand type

Question 3

What is the `nonlocal` keyword used for inside a nested function?

Accepted Answer

To modify a variable defined in the nearest enclosing non-global scope

Answer

To declare a constant that cannot be reassigned

Answer

To import names from an enclosing module's namespace

Answer

To access global variables without writing the global keyword

Question 4

Which attribute of a function object holds the variables captured by its closure?

Accepted Answer

__closure__

Answer

__globals__

Answer

__dict__

Answer

__captured__

Question 5

What will this code output?

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

c = make_counter()
print(c(), c(), c())

Accepted Answer

1 2 3

Answer

0 1 2

Answer

1 1 1

Answer

NameError: name 'count' is not defined

Question 6

What will the following code print?

def outer():
    x = 10
    def inner():
        print(x)
    x = 20
    return inner

f = outer()
f()

Accepted Answer

20

Answer

10

Answer

NameError: name 'x' is not defined

Answer

None

Question 7

Which of the following is the most common practical use case for closures in Python?

Accepted Answer

Factory functions that return specialized functions with pre-configured parameters

Answer

Replacing class-based inheritance hierarchies entirely

Answer

Speeding up loops by caching loop indices

Answer

Catching exceptions without using try/except blocks