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 closure is a nested function that retains access to variables from its enclosing scope, allowing those variables to persist beyond the outer function's lifetime.

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

`outer(5)` returns `inner` with `x` closed over as 5, so calling `add5(3)` computes 5 + 3 = 8.

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

`nonlocal` tells Python that an assignment in the nested function targets the variable in the enclosing scope rather than creating a new local variable.

Question 4

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

Accepted Answer

__closure__

Answer

`func.__closure__` is a tuple of cell objects, each holding the value of one variable captured from the enclosing scope.

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

Each call to `c()` increments the shared `count` variable via `nonlocal`, producing 1, 2, then 3.

PCAP - Certified Associate in Python Programming Practice Test

PCAP - Certified Associate in Python Programming Practice Test

PCAP Closures and Decorators