Welcome to the Python Map, Filter, and Reduce Functions Python Interview Questions! Map, filter, and reduce are powerful built-in functions in Python for functional programming paradigms. These functions allow you to apply a function to each element of a sequence, filter elements based on a condition, and reduce a sequence of elements to a single value. These questions will test your understanding of how to use map, filter, and reduce functions in Python, including their syntax, purpose, and examples. Each question is multiple-choice, with only one correct answer. Take your time to carefully read each question and choose the best option. Let’s explore the world of Python map, filter, and reduce functions together!
30+ Python Interview Questions on Python Map, Filter and Reduce Functions
Q1. What is the purpose of the map() function in Python?
a) To filter elements of a sequence based on a given function
b) To apply a function to every item in an iterable and return a list of the results
c) To reduce an iterable into a single cumulative value
d) To return a subset of elements from an iterable based on a condition
Answer: b
Explanation: The map() function in Python applies a given function to every item in an iterable and returns a list of the results.
Q2. Which of the following is a correct syntax for the map() function in Python?
a) map(function, sequence)
b) map(sequence, function)
c) map(sequence)(function)
d) map(function)(sequence)
Answer: a
Explanation: The correct syntax for the map() function is map(function, sequence) where function is the function to be applied and sequence is the iterable.
Q3. What does the filter() function in Python do?
a) Applies a function to every item in an iterable and returns a single cumulative value
b) Filters out elements of an iterable based on a given function
c) Returns a subset of elements from an iterable based on a condition
d) Maps a function to every item in an iterable and returns a list of the results
Answer: c
Explanation: The filter() function in Python returns a subset of elements from an iterable based on a condition specified by a function.
Q4. Which of the following is a correct syntax for the filter() function in Python?
a) filter(function, sequence)
b) filter(sequence, function)
c) filter(sequence)(function)
d) filter(function)(sequence)
Answer: a
Explanation: The correct syntax for the filter() function is filter(function, sequence) where function is the filtering function and sequence is the iterable.
Q5. What does the reduce() function in Python do?
a) Reduces an iterable into a single cumulative value using a function
b) Applies a function to every item in an iterable and returns a list of the results
c) Filters out elements of an iterable based on a given function
d) Maps a function to every item in an iterable and returns a list of the results
Answer: a
Explanation: The reduce() function in Python reduces an iterable into a single cumulative value by applying a function repeatedly to pairs of items.
Q6. Which module is required to use the reduce() function in Python?
a) math
b) functools
c) itertools
d) operator
Answer: b
Explanation: The reduce() function in Python is part of the functools module, so import functools is required to use it.
Q7. What will be the output of the following code?
from functools import reduce
def multiply(x, y):
return x * y
numbers = [1, 2, 3, 4, 5]
result = reduce(multiply, numbers)
print(result)
a) 15
b) 120
c) 30
d) 10
Answer: b
Explanation: The code will output 120 because reduce() applies the multiply function cumulatively to the items of the numbers list.
Q8. What will the following code snippet do?
numbers = [1, 2, 3, 4, 5]
squared = map(lambda x: x**2, numbers)
a) Creates a list of squares of each number in numbers
b) Filters out even numbers from numbers
c) Reduces numbers into a single cumulative value
d) Raises a syntax error
Answer: a
Explanation: The code creates a map object squared containing the squares of each number in the numbers list.
Q9. Which of the following statements about the lambda function in Python is true?
a) The lambda function can contain multiple expressions.
b) The lambda function can have a return statement.
c) The lambda function can have default arguments.
d) The lambda function can only have a single expression.
Answer: d
Explanation: The lambda function in Python can only have a single expression.
Q10. What will be the output of the following code?
def even_check(num):
if num % 2 == 0:
return True
else:
return False
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = filter(even_check, numbers)
print(list(even_numbers))
a) [1, 3, 5, 7, 9]
b) [2, 4, 6, 8, 10]
c) [True, False, True, False, True, False, True, False, True, False]
d) [2, 4, 6, 8]
Answer: b
Explanation: The code filters out even numbers from the numbers list using the even_check function and prints the resulting list.
Q11. Which of the following is equivalent to the map() function?
a) List comprehension
b) Generator expression
c) Iterator
d) Filter function
Answer: a
Explanation: List comprehension in Python is equivalent to the map() function as it can be used to perform similar tasks of applying a function to every item in an iterable.
Q12. What will be the output of the following code?
def add(a, b):
return a + b
numbers1 = [1, 2, 3, 4]
numbers2 = [5, 6, 7, 8]
sums = map(add, numbers1, numbers2)
print(list(sums))
a) [6, 8, 10, 12]
b) [1, 2, 3, 4, 5, 6, 7, 8]
c) [15, 18, 21, 24]
d) [1, 5, 2, 6, 3, 7, 4, 8]
Answer: a
Explanation: The code creates a map object sums that adds corresponding elements from numbers1 and numbers2, resulting in [6, 8, 10, 12].
Q13. What does the operator module provide in Python?
a) Functions corresponding to built-in operations
b) Functions for creating iterators
c) Functions for sorting lists
d) Functions for mathematical operations
Answer: a
Explanation: The operator module in Python provides functions that correspond to built-in operations, making it useful for map() and reduce() functions.
Q14. What will the following code snippet do?
def is_positive(num):
return num > 0
numbers = [-1, 3, -5, 7, -9]
positive_nums = filter(is_positive, numbers)
a) Create a list of positive numbers from numbers
b) Create a list of negative numbers from numbers
c) Create a list of even numbers from numbers
d) Create a list of all numbers from numbers
Answer: a
Explanation: The code filters out positive numbers from the numbers list using the is_positive function.
Q15. Which function can be used to combine elements of an iterable using a specified function and reduce it to a single value?
a) apply()
b) join()
c) reduce()
d) combine()
Answer: c
Explanation: The reduce() function in Python is used to combine elements of an iterable using a specified function and reduce it to a single value.
Q16. What will be the output of the following code?
from functools import reduce
numbers = [10, 20, 30, 40, 50]
total = reduce(lambda x, y: x + y, numbers)
print(total)
a) 150
b) 100
c) 200
d) 250
Answer: a
Explanation: The code will output 150 because reduce() adds all the numbers in the numbers list together.
Q17. Which of the following statements about the map() function in Python is true?
a) map() always returns a list.
b) map() can only be used with functions that take a single argument.
c) map() can be used with multiple iterables.
d) map() modifies the original iterable.
Answer: c
Explanation: The map() function in Python can be used with multiple iterables, applying the given function to corresponding items.
Q18. What will the following code snippet do?
numbers = [1, 2, 3, 4, 5]
squared = map(lambda x: x**2, numbers)
a) Create a list of squares of each number in numbers
b) Create a list of cubes of each number in numbers
c) Create a list of even numbers from numbers
d) Create a list of all numbers from numbers
Answer: a
Explanation: The code creates a map object squared containing the squares of each number in the numbers list.
Q19. Which function in Python can be used to filter a list of elements based on a given condition?
a) reduce()
b) filter()
c) map()
d) apply()
Answer: b
Explanation: The filter() function in Python is used to filter a list of elements based on a given condition.
Q20. What will be the output of the following code?
def is_even(num):
return num % 2 == 0
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = filter(is_even, numbers)
print(list(even_numbers))
a) [2, 4, 6, 8, 10]
b) [1, 3, 5, 7, 9]
c) [True, False, True, False, True, False, True, False, True, False]
d) [2, 4, 6, 8]
Answer: a
Explanation: The code filters out even numbers from the numbers list using the is_even function and prints the resulting list.
Q21. Which of the following functions can be used to apply a given function to every item of an iterable?
a) reduce()
b) map()
c) filter()
d) apply()
Answer: b
Explanation: The map() function in Python is used to apply a given function to every item of an iterable.
Q22. What will be the output of the following code?
from functools import reduce
numbers = [1, 2, 3, 4, 5]
product = reduce(lambda x, y: x * y, numbers)
print(product)
a) 120
b) 30
c) 15
d) 10
Answer: a
Explanation: The code will output 120 because reduce() multiplies all the numbers in the numbers list together.
Q23. Which of the following is a correct syntax for the reduce() function in Python?
a) reduce(sequence, function)
b) reduce(function, sequence)
c) reduce(sequence)(function)
d) reduce(function)(sequence)
Answer: b
Explanation: The correct syntax for the reduce() function is reduce(function, sequence) where function is the reducing function and sequence is the iterable.
Q24. What will the following code snippet do?
numbers = [10, 20, 30, 40, 50]
doubled = map(lambda x: x * 2, numbers)
a) Create a list of doubled numbers from numbers
b) Create a list of halved numbers from numbers
c) Create a list of even numbers from numbers
d) Create a list of all numbers from numbers
Answer: a
Explanation: The code creates a map object doubled containing the doubled values of each number in the numbers list.
Q25. Which function can be used to apply a function to each element of an iterable and return a list of results?
a) apply()
b) map()
c) filter()
d) reduce()
Answer: b
Explanation: The map() function in Python applies a function to each element of an iterable and returns a list of results.
Q26. What will be the output of the following code?
def is_vowel(char):
vowels = 'aeiouAEIOU'
return char in vowels
chars = ['a', 'b', 'c', 'd', 'e', 'F', 'G', 'H', 'I', 'j']
filtered_chars = filter(is_vowel, chars)
print(list(filtered_chars))
a) [‘a’, ‘e’, ‘F’, ‘I’]
b) [‘a’, ‘e’, ‘I’]
c) [‘a’, ‘e’, ‘A’, ‘E’, ‘I’]
d) [‘a’, ‘e’]
Answer: b
Explanation: The code filters out the vowels from the chars list using the is_vowel function and prints the resulting list.
Q27. What does the operator module provide in Python?
a) Functions corresponding to built-in operations
b) Functions for creating iterators
c) Functions for sorting lists
d) Functions for mathematical operations
Answer: a
Explanation: The operator module in Python provides functions that correspond to built-in operations, making it useful for map() and reduce() functions.
Q28. What will be the output of the following code?
import functools
numbers = [1, 2, 3, 4, 5]
sums = functools.reduce(lambda x, y: x + y, numbers)
print(sums)
a) 15
b) 10
c) 20
d) 25
Answer: a
Explanation: The code will output 15 because reduce() adds all the numbers in the numbers list together.
Q29. What will be the output of the following code?
def cube(num):
return num ** 3
numbers = [1, 2, 3, 4, 5]
cubed = map(cube, numbers)
print(list(cubed))
a) [1, 8, 27, 64, 125]
b) [2, 4, 6, 8, 10]
c) [1, 2, 3, 4, 5]
d) [3, 6, 9, 12, 15]
Answer: a
Explanation: The code will output [1, 8, 27, 64, 125] because map() applies the cube function to each element in numbers.
Q30. What will be the output of the following code?
def square(num):
return num * num
numbers = [1, 2, 3, 4, 5]
squared = map(square, numbers)
print(list(squared))
a) [1, 4, 9, 16, 25]
b) [2, 4, 6, 8, 10]
c) [1, 3, 5, 7, 9]
d) [1, 2, 3, 4, 5]
Answer: a
Explanation: The code will output [1, 4, 9, 16, 25] because map() applies the square function to each element in numbers.
Q31. What will be the output of the following code?
from functools import reduce
def multiply(x, y):
return x * y
numbers = [1, 2, 3, 4, 5]
product = reduce(multiply, numbers, 10)
print(product)
a) 150
b) 120
c) 100
d) 200
Answer: b
Explanation: The code will output 120 because reduce() multiplies all the numbers in the numbers list together starting with an initial value of 10.
Congratulations on completing the Python Map, Filter, and Reduce Functions MCQs! Map, filter, and reduce functions are powerful tools for functional programming in Python, allowing you to apply transformations and operations to sequences of elements. By mastering these functions, you gain the ability to write concise and efficient code for data manipulation tasks. Keep practicing and experimenting with map, filter, and reduce functions to become proficient in using them effectively. If you have any questions or want to delve deeper into any topic, don’t hesitate to continue your learning journey. Happy coding!
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