map() for element-wise mapping in Data Analysis Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of map() with a lambda function

What is the output of this Python code using map()?

Data Analysis Python

numbers = [1, 2, 3, 4]
result = list(map(lambda x: x**2, numbers))
print(result)

A [2, 3, 4, 5]

B [1, 4, 9, 16]

C [1, 8, 27, 64]

D [1, 2, 3, 4]

💡 Hint

Remember, map() applies the function to each element in the list.

The lambda function squares each number. So 1²=1, 2²=4, 3²=9, 4²=16.

❓ data_output

intermediate

Mapping a dictionary to a list

What is the output of this code that uses map() on a dictionary's keys?

Data Analysis Python

data = {'a': 1, 'b': 2, 'c': 3}
result = list(map(str.upper, data))
print(result)

A ['a', 'b', 'c']

B ['1', '2', '3']

C ['A', 'B', 'C']

D ['A', 'B', 'C', 'D']

💡 Hint

Mapping applies to dictionary keys by default.

The map() applies str.upper to each key: 'a' → 'A', 'b' → 'B', 'c' → 'C'.

🔧 Debug

advanced

Identify the error in map() usage

What error does this code raise when run?

Data Analysis Python

values = [1, 2, 3]
result = list(map(lambda x: x + y, values))
print(result)

A NameError: name 'y' is not defined

B TypeError: unsupported operand type(s) for +: 'int' and 'function'

C SyntaxError: invalid syntax

D No error, output is [2, 3, 4]

💡 Hint

Check if all variables inside the lambda are defined.

The variable 'y' is not defined anywhere, so Python raises a NameError.

🚀 Application

advanced

Using map() to convert string numbers to integers

Given a list of strings representing numbers, which option correctly converts them to integers using map()?

Data Analysis Python

str_numbers = ['10', '20', '30', '40']

A list(map(float, str_numbers))

B list(map(str, str_numbers))

C list(map(lambda x: x + 1, str_numbers))

D list(map(int, str_numbers))

💡 Hint

You want to convert strings to integers, not to strings or floats.

Using int converts each string to an integer. Other options either keep strings or convert to float.

🧠 Conceptual

expert

Behavior of map() with multiple iterables

What is the output of this code using map() with two lists?

Data Analysis Python

a = [1, 2, 3]
b = [4, 5, 6]
result = list(map(lambda x, y: x + y, a, b))
print(result)

A [5, 7, 9]

B [1, 2, 3, 4, 5, 6]

C [4, 10, 18]

D TypeError: <lambda>() missing 1 required positional argument

💡 Hint

When multiple iterables are passed, map applies the function to pairs of elements.

The lambda adds elements from both lists pairwise: 1+4=5, 2+5=7, 3+6=9.