Built-in scope in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of shadowing a built-in function

What is the output of this code?

len = 5
print(len([1, 2, 3]))

Python

len = 5
print(len([1, 2, 3]))

A NameError

B 3

C TypeError

D 5

💡 Hint

Think about what happens when you assign a number to the name 'len'.

The variable 'len' is assigned the number 5, so it no longer refers to the built-in function. When you try to call 'len([1, 2, 3])', it tries to call the integer 5 as a function, causing a TypeError.

❓ Predict Output

intermediate

Using built-in function after local shadowing

What is the output of this code?

def f():
    sum = 10
    return sum([1, 2, 3])

print(f())

Python

def f():
    sum = 10
    return sum([1, 2, 3])

print(f())

A TypeError

B NameError

C 6

D 10

💡 Hint

Inside the function, what does 'sum' refer to?

Inside the function, 'sum' is a local variable assigned to 10, so calling 'sum([1, 2, 3])' tries to call the integer 10 as a function, causing a TypeError.

🔧 Debug

advanced

Why does this code raise an error?

This code raises an error. What is the cause?

min = 5
numbers = [3, 1, 4]
print(min(numbers))

Python

min = 5
numbers = [3, 1, 4]
print(min(numbers))

A min is an integer, so calling min(numbers) causes TypeError

B min is not defined, causing NameError

C numbers is not iterable, causing TypeError

D SyntaxError due to missing colon

💡 Hint

Check what 'min' refers to after assignment.

Assigning 5 to 'min' shadows the built-in function 'min'. Calling 'min(numbers)' tries to call the integer 5 as a function, causing a TypeError.

❓ Predict Output

advanced

Output when using built-in after deleting local shadow

What is the output of this code?

max = 10
print(max)
del max
print(max([1, 5, 3]))

Python

max = 10
print(max)
del max
print(max([1, 5, 3]))

A TypeError\n5

B 10\n5

C TypeError\nTypeError

D 10\nTypeError

💡 Hint

What happens after deleting the local variable 'max'?

First, print(max) prints 10 because 'max' refers to the integer 10 (shadowing the built-in). After 'del max', the name refers back to the built-in function, so print(max([1, 5, 3])) outputs 5.

❓ Predict Output

expert

Output of nested function with built-in shadowing

What is the output of this code?

def outer():
    list = "not a list"
    def inner():
        return list([1, 2, 3])
    return inner()

print(outer())

Python

def outer():
    list = "not a list"
    def inner():
        return list([1, 2, 3])
    return inner()

print(outer())

A [1, 2, 3]

B SyntaxError

C NameError

D TypeError

💡 Hint

What does 'list' refer to inside inner()? Is it a function?

The variable 'list' in outer shadows the built-in 'list' function. Inside inner(), 'list' refers to the string 'not a list'. Calling 'list([1, 2, 3])' tries to call a string as a function, causing a TypeError.