Lambda with map() in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to double each number in the list using map and a lambda function.

Python

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

Drag options to blanks, or click blank then click option'

A*

B+

C-

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of * will add 2 instead of doubling.

Using / will divide the number by 2, not double it.

The lambda function multiplies each number by 2 using the * operator.

2fill in blank

medium

Complete the code to convert each string in the list to uppercase using map and a lambda.

Python

words = ['apple', 'banana', 'cherry']
upper_words = list(map(lambda w: w[1](), words))
print(upper_words)

Drag options to blanks, or click blank then click option'

Alower

Bcapitalize

Cupper

Dtitle

Attempts:

3 left

💡 Hint

Common Mistakes

Using lower() will convert to lowercase instead.

Using capitalize() only changes the first letter.

The lambda calls the upper() method to convert each word to uppercase.

3fill in blank

hard

Fix the error in the lambda function to add 5 to each number using map.

Python

nums = [10, 20, 30]
result = list(map(lambda n: n [1] 5, nums))
print(result)

Drag options to blanks, or click blank then click option'

A-

B*

C/

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using - subtracts 5 instead of adding.

Using * multiplies instead of adding.

The lambda should add 5 to each number using the + operator.

4fill in blank

hard

Fill both blanks to create a list of squares of even numbers only using map and filter with lambda.

Python

numbers = [1, 2, 3, 4, 5, 6]
even_squares = list(map(lambda x: x[1]2, filter(lambda x: x [2] 2 == 0, numbers)))
print(even_squares)

Drag options to blanks, or click blank then click option'

A**

B%

C//

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using + or // instead of ** for squaring.

Using // or + instead of % for checking evenness.

The first lambda squares the number using **. The second lambda filters even numbers using the modulo operator %.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values doubled only if value is greater than 10.

Python

data = {'a': 5, 'b': 15, 'c': 20}
result = { [1]: [2]*2 for k, v in data.items() if v [3] 10 }
print(result)

Drag options to blanks, or click blank then click option'

Ak.upper()

Bv

C>

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using k instead of k.upper() for keys.

Using v without doubling.

Using < or == instead of > in the condition.

The dictionary comprehension uses k.upper() for keys, doubles the value v, and filters values greater than 10 with >.

Practice

1.

What does the map() function do when used with a lambda in Python?

easy

A. Creates a new list without changing items

B. Filters items based on a condition

C. Applies the lambda function to each item in the list

D. Sorts the list items

Solution

1. Step 1: Understand the role of map()

   map() takes a function and a list, then applies the function to each item.

2. Step 2: Role of lambda with map()

   The lambda defines a quick function to apply to each item in the list.

3. Final Answer:

   Applies the lambda function to each item in the list -> Option C

4. Quick Check:

   map() + lambda = apply function to each item [OK]

Hint: Remember: map applies function to every list item [OK]

Common Mistakes:

• Thinking map filters items
• Assuming map sorts the list
• Believing map returns the original list unchanged

2.

Which of the following is the correct syntax to double each number in the list [1, 2, 3] using map() and lambda?

?

easy

A. map(lambda x: x * 2, [1, 2, 3])

B. list(map(lambda x: x * 2, [1, 2, 3]))

C. list(lambda x: x * 2, [1, 2, 3])

D. map([1, 2, 3], lambda x: x * 2)

Solution

1. Step 1: Check map() syntax

   map() takes a function first, then the iterable (list).

2. Step 2: Convert map object to list

   To see results, wrap map() with list().

3. Final Answer:

   list(map(lambda x: x * 2, [1, 2, 3])) -> Option B

4. Quick Check:

   Correct syntax = list(map(lambda x: x * 2, list)) [OK]

Hint: Use list() around map() to see results [OK]

Common Mistakes:

• Forgetting to convert map to list
• Swapping arguments in map()
• Using lambda outside map() incorrectly

3.

What is the output of the following code?

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

medium

A. [2, 3, 4, 5]

B. [1, 2, 3, 4]

C. [0, 1, 2, 3]

D. Error

Solution

1. Step 1: Understand the lambda function

   The lambda adds 1 to each number in the list.

2. Step 2: Apply lambda to each item in nums

   Each number 1,2,3,4 becomes 2,3,4,5 respectively.

3. Final Answer:

   [2, 3, 4, 5] -> Option A

4. Quick Check:

   Each item +1 = [2,3,4,5] [OK]

Hint: Add 1 to each item with lambda x: x + 1 [OK]

Common Mistakes:

• Forgetting to convert map to list before print
• Confusing addition with multiplication
• Expecting original list unchanged

4.

Find the error in this code snippet:

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

medium

A. map() requires two arguments but only one given

B. Lambda syntax is incorrect

C. List 'numbers' is not defined

D. Missing list() to convert map object before printing

Solution

1. Step 1: Check map() usage

   map() returns a map object, not a list.

2. Step 2: Printing map object directly

   Printing map object shows memory address, not values; convert to list first.

3. Final Answer:

   Missing list() to convert map object before printing -> Option D

4. Quick Check:

   Use list() to see map results [OK]

Hint: Wrap map() with list() before printing [OK]

Common Mistakes:

• Trying to print map object directly
• Thinking lambda syntax is wrong
• Assuming map needs more arguments

5.

You have a list of strings representing numbers: ['1', '2', '3', '4']. Using map() and lambda, how do you convert this list to integers and then add 10 to each number?

hard

A. list(map(lambda x: int(x) + 10, ['1', '2', '3', '4']))

B. list(map(lambda x: x + 10, ['1', '2', '3', '4']))

C. list(map(int(x) + 10, ['1', '2', '3', '4']))

D. list(map(lambda x: int(x + 10), ['1', '2', '3', '4']))

Solution

1. Step 1: Convert strings to integers inside lambda

   Use int(x) to convert each string to an integer.

2. Step 2: Add 10 to each converted integer

   Inside lambda, add 10 to the integer value.

3. Final Answer:

   list(map(lambda x: int(x) + 10, ['1', '2', '3', '4'])) -> Option A

4. Quick Check:

   Convert then add 10 = list(map(lambda x: int(x)+10, list)) [OK]

Hint: Convert string to int inside lambda before adding [OK]

Common Mistakes:

• Adding 10 to string without conversion
• Incorrect lambda syntax
• Trying to call int() outside lambda in map