Enclosing scope in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested function accessing enclosing variable

What is the output of this code?

Python

def outer():
    x = 5
    def inner():
        return x + 3
    return inner()

result = outer()
print(result)

A 8

B TypeError

C 5

D NameError

💡 Hint

Remember that inner functions can access variables from their enclosing function.

The inner function accesses the variable x from the outer function's scope and adds 3, so 5 + 3 = 8.

❓ Predict Output

intermediate

Effect of modifying enclosing variable without nonlocal

What is the output of this code?

Python

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

print(outer())

A None

B 10

C UnboundLocalError

D 20

💡 Hint

Assigning to x inside inner creates a new local variable, not changing outer's x.

The assignment inside inner creates a new local x, so outer's x remains 10.

❓ Predict Output

advanced

Using nonlocal to modify enclosing variable

What is the output of this code?

Python

def outer():
    x = 1
    def inner():
        nonlocal x
        x += 5
    inner()
    return x

print(outer())

A UnboundLocalError

B 1

C SyntaxError

D 6

💡 Hint

The nonlocal keyword allows inner to modify x in the outer scope.

nonlocal x lets inner modify the x defined in outer, so x becomes 1 + 5 = 6.

❓ Predict Output

advanced

Output when accessing variable before assignment in nested function

What error does this code raise?

Python

def outer():
    x = 3
    def inner():
        print(x)
        x = 5
    inner()

outer()

A UnboundLocalError

B NameError

C SyntaxError

D 3

💡 Hint

Assigning to x inside inner makes x local, so print(x) tries to access before assignment.

Python treats x as local in inner due to assignment, so print(x) before assignment causes UnboundLocalError.

🧠 Conceptual

expert

How many items in the list after closure creation?

Consider this code that creates a list of functions inside a loop. How many functions in the list will return the value 4 when called?

Python

def make_funcs():
    funcs = []
    for i in range(5):
        def f():
            return i
        funcs.append(f)
    return funcs

funcs = make_funcs()
results = [func() for func in funcs]
print(results.count(4))

A 0

B 1

C 5

D 4

💡 Hint

All functions capture the same variable i, which after the loop ends is 4.

All functions refer to the same i, which is 4 after the loop, so all return 4, count is 5.