Python Practice Questions & Solutions Day 6 of Learning Python for Data Science

Welcome back to Day 6 of Learning Python for Data Science journey! In the last article, we explored:

✅ Lists
✅ Tuples
✅ Sets
✅ Dictionaries

Now, it’s time to solve the practice questions given in the previous article.
Each question is followed by a detailed explanation and output.

Create a list of five student names and print it.

student = ['Jacob', 'Jenny', 'John', 'Julie']

print(student)

Output

['Jacob', 'Jenny', 'John', 'Julie']

Add a new student name to the end of the list using the appropriate method.

student.append('Mark')
print(student)

Output

['Jacob', 'Jenny', 'John', 'Julie', 'Mark']

Insert a student name at the second position in the list.

student.insert(1, "David")
print(student)

Output

['Jacob', 'David', 'Jenny', 'John', 'Julie', 'Mark']

Remove a specific student name from the list.

student.remove('David')
print(student)

Output

['Jacob', 'Jenny', 'John', 'Julie', 'Mark']

Remove and return the last element of the list.

removed = student.pop()
print('Removed: ', removed) 

Output

Removed:  Mark

Retrieve a sublist containing elements from index 2 to 4 using slicing.

sublist = student[2:5]
print(sublist)

Output

['John', 'Julie']

Find the index of a specific student name in the list.

index = student.index('Julie')
print(index)

Output

3

Sort a list of integers in ascending order.

numbers = [5, 2, 9, 1, 5, 6]
numbers.sort()
print(numbers)

Output

[1, 2, 5, 5, 6, 9]

Reverse the order of elements in a list.

numbers.reverse()
print(numbers)

Output

[9, 6, 5, 5, 2, 1]

Count the number of times a specific element appears in a list.

count = numbers.count(5)
print('5 appears ',count,' times in the list' )

Output

5 appears  2  times in the list

Find the length of a given list.

length = len(numbers)
print(length)

Output

6

Create a set containing five unique numbers and print it.

num = {23, 45, 67, 89, 78}
print(num)

Output

{67, 23, 89, 45, 78}

Add a new element to the set.

num.add(34)
print(num)

Output

{34, 67, 23, 89, 45, 78}

Try adding a duplicate element to the set and observe the output.

num.add(34)
print(num)

Output

{34, 67, 23, 89, 45, 78}
Set does not store duplicates and removes them.

Remove an element from the set using the appropriate method.

num.remove(34)
print(num) # removed 34

Output

{67, 23, 89, 45, 78}

Perform a union operation between two sets and print the result.

num1 = {12, 23, 34, 12, 34, 45, 67}
num2 = {12, 23, 78, 89, 67, 56, 22}

union = num1.union(num2)
print(union)

Output

{34, 67, 12, 45, 78, 22, 23, 56, 89}

Find the common elements between two sets using the intersection method.

common = num1.intersection(num2)
print(common)

Output

{67, 12, 23}

Find the elements that exist in the first set but not in the second set using the difference method.

difference = num1.difference(num2)
print(difference)

Output

{34, 45}

Check if one set is a subset of another set.

is_subset = num1.issubset(num2)
print(is_subset)

Output

False

Check if two sets have no common elements using the appropriate method.

print('num1: ',num1)
print('num2: ',num2)
print(num1.isdisjoint(num2))

Output

num1:  {34, 67, 23, 12, 45}
num2:  {67, 22, 23, 56, 89, 12, 78}
False

Write a Python program to count the number of occurrences of each element in a given list.

el = ['R', 'R', 'R', 'S', 'S', 'Sh', 'Sh']

count = {}  

for i in el:  
    if i in count:
        count[i] += 1  
    else:
        count[i] = 1  
        
print(count)

Output

{'R': 3, 'S': 2, 'Sh': 2}

Create a set of numbers from 1 to 10. Find all the numbers that are divisible by 3 using a set operation.

nums = {i for i in range(1,11) if i%3 == 0}

print(nums)

Output

{9, 3, 6}

Given two lists of integers, write a program to find the elements that are common in both lists using a set.

set1 = [1, 2, 3, 4, 5, 6]
set2 = [3, 4, 5, 6, 7, 8]

set(set1).intersection(set2)

Output

{3, 4, 5, 6}

Write a program to remove duplicate words from a given string and display the unique words in alphabetical order.

string = ' the boy is quite a boy'

string = set(string.split())

unique = []

result = [i for i in string if i not in unique]

print(result)

Output

['the', 'a', 'is', 'quite', 'boy']

Create a list of mixed data types (e.g., numbers and strings). Write a program to separate the strings and numbers into two different lists.

l = [1, 2, 3, 4, 5, 6, 'R', 'R', 'R', 'S', 'S', 'Sh', 'Sh']

numbers = []
strings= []

for i in l:
    if isinstance(i, str):
        strings.append(i)
    else:
        numbers.append(i)

print(numbers, strings)

Write a function that returns the second largest number from a list of integers. Example: [10, 20, 4, 45, 99] → Output: 45

num = [10, 20, 4, 45, 99]
num.sort(reverse=True)
print(num)
print('Second largest number is: ',num[1])

Output

[99, 45, 20, 10, 4]
Second largest number is:  45

Given a list and an integer k, shift elements to the right by k positions. Example: ([1, 2, 3, 4, 5], k=2) → Output: [4, 5, 1, 2, 3]

list1 = [1, 2, 3, 4, 5]
k = 2
new_list = list1[k:] + list1[:k]
print(new_list)

Output

[3, 4, 5, 1, 2]

Given a list, remove duplicate elements while maintaining the order. Example: [1, 2, 2, 3, 4, 4, 5] → Output: [1, 2, 3, 4, 5]

l = [1, 2, 2, 3, 4, 4, 5]
l1 = []
[l1.append(i) for i in l if i not in l1]
print(l1)

Output

[1, 2, 3, 4, 5]

Given a list and a target sum, find all unique pairs whose sum equals the target. Example: ([1, 2, 3, 4, 5, 6], target=7) → Output: [(1, 6), (2, 5), (3, 4)]

# method 1
lis = [1, 2, 3, 4, 5, 6]
target = 7
result = []

for i in lis:
    for j in lis:
        if i + j == target and (j, i) not in result:
            result.append((i, j))

print(result)

# method 2
re = []
[re.append((i, j)) for i in lis for j in lis if i + j == target and (j, i) not in re]
re

Output

[(1, 6), (2, 5), (3, 4)]

Implement a function that finds the index of a given element in a list manually. Example: ([10, 20, 30, 40], target=30) → Output: 2

# defining the function
def position(lis, target):
    for i, el in enumerate(lis):
        if el == target:
            return i     
 
# test data 
lis = [10, 20, 30, 40]
target = 30

# calling the function
position(lis, target)

Output

2

Write a function that returns elements that exist in either of the two sets but not both. Example: {1, 2, 3, 4} and {3, 4, 5, 6} → Output: {1, 2, 5, 6}

set1 = {1, 2, 3, 4}
set2 = {3, 4, 5, 6}

set1.symmetric_difference(set2)

Output

{1, 2, 5, 6}

Given two sets, determine if one set is a subset of the other. Example: {1, 2} is a subset of {1, 2, 3, 4} → Output: True

set1 = {1, 2, 3, 4}
set2 = {3, 4, 5, 6}
set1.issubset(set2)

Output

False

set1 = {1,2}
set2 = {1,2,3,4,5}
set1.issubset(set2)

Output

True

Given multiple sets, find the total count of unique elements across all sets. Example: [{1, 2, 3}, {3, 4, 5}, {5, 6, 7}] → Output: 7

sets = [{1, 2, 3}, {3, 4, 5}, {5, 6, 7}]
set1 = sets[0].union(sets[1]).union(sets[2])
print('total count of unique elements across all sets is : ',len(set1))

Output

total count of unique elements across all sets is:  7

Given three sets, find the elements that are common in all three. Example: {1, 2, 3}, {2, 3, 4}, {3, 4, 5} → Output: {3}

set1 = {1, 2, 3}
set2 = {2, 3, 4}
set3 = {3, 4, 5}

common = set1.intersection(set2).intersection(set3)

print('element that is common in all three: ',common)

Output

element that is common in all three:  {3}

Remove all elements of set2 from set1 without using a loop. Example: {1, 2, 3, 4, 5} minus {3, 4} → Output: {1, 2, 5}

set1 = {1, 2, 3, 4, 5}
set2 = {3, 4}

set1.difference(set2) #1
set1-set2 #2

Output

{1, 2, 5}

Given a list of integers, find the length of the longest consecutive elements sequence. Example: [100, 4, 200, 1, 3, 2] → Output: 4 ([1, 2, 3, 4] is the longest sequence)¶

lis = [100, 4, 200, 1, 3, 2]
re = []
final = []
for i in lis:
    if i-1 in lis or i == min(lis):
      re.append(i)
re

Output

[4, 1, 3, 2]

Rearrange a sorted list so that the first element is the smallest, the second is the largest, the third is the second smallest, and so on. Example: [1, 2, 3, 4, 5, 6, 7] → Output: [1, 7, 2, 6, 3, 5, 4]

lis = [1, 2, 3, 4, 5, 6, 7] 
output = []

while len(lis)>1:
    min_val = min(lis)
    max_val = max(lis)
    
    output.append(min_val)
    output.append(max_val)
    lis.remove(min_val)
    lis.remove(max_val)

if lis:
    output.append(lis[0])
    
output

Output

[1, 7, 2, 6, 3, 5, 4]

An element is a majority if it appears more than n/2 times in a list of size n. Find it in O(n) time. Example: [3, 3, 4, 2, 4, 4, 2, 4, 4] → Output: 4

def majority_element(nums):
    candidate, count = None, 0

    # Step 1: Find candidate
    for num in nums:
        if count == 0:
            candidate = num
        count += (1 if num == candidate else -1)

    # Step 2: Verify candidate
    if nums.count(candidate) > len(nums) // 2:
        return candidate
    return None  # No majority element found

# Example usage
lis = [3, 3, 4, 2, 4, 4, 2, 4, 4]
print(majority_element(lis))

Output

4

Given two sets of numbers, find all pairs (a, b) where a is from set1, b is from set2, and (a + b) is even. Example: {1, 2, 3} and {4, 5, 6} → Output: {(2, 4), (2, 6), (1, 5), (3, 5)}

set1 = {1, 2, 3}
set2 = {4, 5, 6}

set3 = set()
for a in set1:
    for b in set2:
        if (a + b) % 2 == 0:
            set3.add((a, b))

print(set3)

Output

{(2, 4), (2, 6), (3, 5), (1, 5)}

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