DEV Community: Keerti Sadana S

PYTHON - SET

Keerti Sadana S — Thu, 01 Oct 2026 18:33:38 +0000

-> A Set in Python is a collection of unique items.
->It is an unordered collection that does not allow duplicate entries. Sets are primarily used for membership testing and eliminating duplicates from a sequence.
-> It is mutable.
-> Set can be created by set() and {v1,v2,...vn}.
-> {} means a dictionary.

Mathematical Operations:
union, intersection, difference

s1 = {10,20,30,40}
s2 = {30,40,70,80}
print(s1.union(s2))
print(s1 | s2)

print(s1.intersection(s2))
print(s1 & s2)

print(s1.difference(s2))
print(s1 - s2)

print(s1.symmetric_difference(s2))
print(s1 ^ s2)

Output:
{70, 40, 10, 80, 20, 30}
{70, 40, 10, 80, 20, 30}
{40, 30}
{40, 30}
{10, 20}
{10, 20}
{70, 10, 80, 20}
{70, 10, 80, 20}

remove() vs clear() vs pop():

s = {'Hi', True, 5}
s.remove('Hi')
print(s)
print(s.pop())
print(s)
s.clear()
print(s)

Output:
{5, True}
5
{True}
set()

discard():
-> In Python, the discard() method removes a specified element from a set.
-> If the element is not found, it won't return an error

s = {'Hi', 10,20, True}
s.remove('Hi')
print(s)
s.discard('Hello')
print(s)

Output:
{True, 10, 20}
{True, 10, 20}

PYTHON - TUPLE

Keerti Sadana S — Thu, 01 Oct 2026 18:08:42 +0000

-> A tuple in Python is a built-in collection data type used to store multiple items in a single variable.
-> It is characterised by being ordered, immutable (unchangeable), and allowing duplicate values
-> Similar to List
-> Insertion Order is maintained
-> Duplicate elements are allowed
-> Performance - Tuple is good

t = (10,20,30,40,50)
t2 = ()
print(type(t2))
t3 = (10)
print(type(t3))
t4 = (10,)
print(type(t4))

Output:

t1 = (10,20,30)
t2 = (40,50,60)
t3 = t1 + t2
print(t3)
print(t1*2)
print(100 in t1)
print(100 not in t1)

Output:
(10, 20, 30, 40, 50, 60)
(10, 20, 30, 10, 20, 30)
False
True

Tuple Comprehension:

numbers = (no for no in range(1,11))
print(numbers) #generator object

Output:
at 0x000001D88B691A80>

Packing and Unpacking:

t = 10,20,30
print(type(t))
no1, no2, no3 = t
print(no1)
print(no2)
print(no3)

Output:

10
20
30

eval():
-> The eval() function in Python is a built-in tool that dynamically parses, compiles, and evaluates a string as a Python expression.

t = eval(input("Enter tuple elements: "))
print(t)
total = 0 
for num in t:
    total+=num
print(total)

Output:
Enter tuple elements: 10,20,30,50
(10, 20, 30, 50)
110

*Performance: *

import sys
l = [10,20,30]
t = (10,20,30)
print(sys.getsizeof(l)) #Dynamic Sizing -> Mutability
print(sys.getsizeof(t))

Output:
88
64

PYTHON - LIST COMPREHENSIVE TASKS

Keerti Sadana S — Wed, 30 Sep 2026 17:03:06 +0000

Task 1:

no1 = [10,20,30,40]
no2 = [30,40,50,60]
common_list = [i for i in no1 if i in no2]
unique_list = [i for i in no1 if i not in no2]+[j for j in no2 if j not in no1]
print(common_list)
print(unique_list)

Output:
[30, 40]
[10, 20, 50, 60]

Task 2:

no1 = [1,2,3]
no2 = [6,7,8]
comb = [[i,j] for i in no1 for j in no2]
print(comb)

Output:
[[1, 6], [1, 7], [1, 8], [2, 6], [2, 7], [2, 8], [3, 6], [3, 7], [3, 8]]

*Task 3: *

list = [i**2 for i in range(1,11) if i%2 == 0]
print(list)

Output:
[4,16,36,64,100]

Task 4:

matrix = [[10,20,30], [40,50,60], [70,80,90]]
list = [j for i in matrix for j in i]
print(list)

Output:
[10,20,30,40,50,60,70,80,90]

PYTHON - LIST COMPREHENSIVE

Keerti Sadana S — Wed, 30 Sep 2026 15:56:54 +0000

List comprehension:
-> List comprehension is a concise way to create new lists by applying an expression to each item in an existing iterable, like a list, tuple or range.
-> Example:

l = [no*no for no in range(1,11)]
print(l)

Output:
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

WHY List Comprehension:
1) Concise Code
2) Readability
3) Efficiency: (better than normal for loops - Optimized code)

PYTHON - LIST TASK 2

Keerti Sadana S — Fri, 25 Sep 2026 18:45:41 +0000

1) Find max, second max from a given list

l1 = [100,28,46,78]
max = l1[0]
for i in l1:
    if i > max:
        max = i
print(max)
l1 = [28,46,78,100]
max = l1[0]
second_max = 0
for i in l1:
    if i >= max:
        second_max = max
        max = i
print(second_max)

Output:
100
78

2) Find min, second min from a given list

l1 = [100,28,46,78]
min = l1[0]
for i in l1:
    if i <= min:
        min = i
print(min)
l1 = [100,46,78,28]
min = l1[0]
second_min = 0
for i in l1:
    if i <= min:
        second_min = min
        min = i
print(second_min)

Output:
28
46

3) Reverse a list without using reverse()

l1 = [100,28,48,69]
rev = []
i = len(l1)-1
while i>=0:
    rev.append(l1[i])
    i-=1
print(rev)

Output:
[69, 48, 28, 100]

4) Confirm if a given list is palindrome or not:

l1 = [10,20,30,20,10]
l2 = l1[::-1]
print(l1==l2)

Output:
True

5) Remove duplicate elements from a list:

l1 = [10,20,30,20,10]
l2 = []
for i in l1:
    if i not in l2:
        l2.append(i)
print(l2)

Output:
[10,20,30]

6) Find pairs with a given sum:

sumval = 6
pair = []
l1 = [1,5,2,4,3,7,8,6,0]
for i in range(len(l1)):
    for j in range(i+1,len(l1)):
        if l1[i]+l1[j] == 6:
            pair.append((l1[i],l1[j]))
print(pair)

Output:
[(1, 5), (2, 4), (6, 0)]

isinstance():
isinstance() is a built-in function used to check if an object belongs to a specific class, type, or a subclass of that class.

7) Print only str elements from a given list:

l1 = [10,20,True, False, 5.4, 'abcd', 'pqrs']
for i in l1:
    if isinstance(i,str):
        print(i)

Output:
abcd
pqrs

8) Find the missing number in a list of 1 to n:

l = [1,2,3,4,5,6,8,9,10]
i = 0
j = 1
while i<len(l)-1:
    if l[j]-l[i] == 1:
        pass
    else:
        print(l[j]-1)
    i+=1
    j+=1

Output:
7

9) Nested List: Flattening a nested list:

def flatten_list(l):
    flat = []
    for i in l:
        if isinstance(i,list):
            flat.extend(flatten_list(i))
        else:
            flat.append(i)
    return flat
nested_list = [1, [2, [3,4], 5], 6]
print(flatten_list(nested_list))

Output:
[1,2,3,4,5,6]

PYTHON - REVERSE(),SORT(),COPY() AND COUNT()

Keerti Sadana S — Fri, 25 Sep 2026 18:04:44 +0000

Python List Reverse():
-> The reverse() method is a built-in method in Python that reverses the order of elements in a list.
-> This method modifies the original list and does not return a new list, which makes it an efficient way to perform the reversal without unnecessary memory uses.

a = [1, 2, 3, 4, 1, 2, 6] 
a.reverse() 
print(a)

Output:
[6, 2, 1, 4, 3, 2, 1]

Sort():
-> The sort() method in Python is used to arrange the elements of a list in a specific order.
-> It works only on lists, modifies the original list in place, and does not return a new list.

a = [5, 3, 8, 1, 2]
a.sort()
print(a)

Output:
[1, 2, 3, 5, 8]

sort vs sorted:
sort --> in-place sorting: The original list gets modified.
sorted --> returns a new list with elements sorted.

Copy():
-> The copy() method in Python is used to create a shallow copy of a list.
-> This means that the method creates a new list containing the same elements as the original list but maintains its own identity in memory.
-> It's useful when you want to ensure that changes to the new list do not affect the original list and vice versa.

a = [1, 2, 3]
b = a.copy()
print('a:', a)
print('b:', b)

Output:
a: [1, 2, 3]
b: [1, 2, 3]

Count():
-> The count() method in Python returns the number of times a specified substring appears in a string.
-> It is commonly used in string analysis to quickly check how often certain characters or words appear.

s = "hello world"
res = s.count("o")
print(res)
s = "hello world"
res = s.count("o")
print(res)

Output:
2

PYTHON - DEL(), REMOVE() AND POP()

Keerti Sadana S — Fri, 25 Sep 2026 17:23:03 +0000

del():
-> del is a Python keyword used to delete items from a list by index or to remove the entire list.
-> With del, we can specify a single element by index or use slicing to delete a range of elements.

a = [1, 2, 3, 2, 3, 4, 5]
del a[3]
print(a)
a = [1, 2, 3, 2, 3, 4, 5]
del a[1:3]
print(a)

Output:
[1, 2, 3, 3, 4, 5]
[1, 2, 3, 4, 5]

remove():
The remove() method removes the first matching value from the list. It requires the value we want to remove from list as its argument.

a = [1, 2, 3, 2, 3, 4, 5]
a.remove(3)
print(a)

Output:
[1, 2, 2, 3, 4, 5]

pop():
-> The pop() method removes and returns an element from the list.
-> By default, it removes the last element, but we can specify an index to remove an element at a particular position.

a = [1, 2, 3, 2, 3, 4, 5]
a.pop(3)
print(a)

Output:
[1, 2, 3, 3, 4, 5]

del() VS remove() vs pop():

PYTHON - LIST TASK

Keerti Sadana S — Mon, 21 Sep 2026 17:16:36 +0000

1) Print q, h, a marks in separate lines

q = [90,87,65,67,89]
h = [96,97,95,69,99]
a = [99,98,100,76,49]

marks = [q,h,a]
i = 0
while i<len(marks):
    print(marks[i])
    i+=1

Output:
[90, 87, 65, 67, 89]
[96, 97, 95, 69, 99]
[99, 98, 100, 76, 49]

2) Calculate the total and Percentage of q, h and a

q = [90,87,65,67,89]
h = [96,97,95,69,99]
a = [99,98,100,76,49]
mark = [q,h,a]
no = len(mark[0])
k = 1
for i in mark:
    total = 0
    for j in i:
        total+=j
    print(f'Total of sublist {k} = {total}')
    print(f'Percent of sublist {k} = {(total*100)//(no*100)}%')
    k+=1

3) Calculate Average of Tamil (first subject)

q = [90,87,65,67,89]
h = [96,97,95,69,99]
a = [99,98,100,76,49]
mark = [q,h,a]
total = 0
for i in mark:
    total += i[0]
print(f'Average of Tamil = {total/len(mark)}')

Output:
Average of Tamil = 95.0

4) Calculate highest total among these three

q = [90,87,65,67,89]
h = [96,97,95,69,99]
a = [99,98,100,76,49]
mark = [q,h,a]
no = len(mark[0])
high = 0
k = 1
for i in mark:
    total = 0
    for j in i:
        total+=j
    if total>high:
        high = total
        index = k
    k+=1
print(f'substring {index} is high')

Output:
substring 2 is high

PYTHON - APPEND(),INSERT() AND EXTEND()

Keerti Sadana S — Mon, 21 Sep 2026 16:07:21 +0000

Append:
The append() method in Python is used to add a single element to the end of a list.

Example:

l=[]
l.append('abcd')
l.append(1234)
l.append(True)
l.append(5.4)
print(l)

Output:
['abcd', 1234, True, 5.4]

Insert:
-> To insert an item at a specific position in a Python list, use the list.insert(index, element) method.
-> This method modifies the original list in place and does not return a new list.

Example:

l = ['abcd',1234,True, 5.4]

l.insert(1, 'dhanush')
print(l)

l.insert(-2, 'vinoth m')
print(l)

l.insert(-101, 'akilan')
print(l)

Output:
['abcd', 'dhanush', 1234, True, 5.4]
['abcd', 'dhanush', 1234, 'vinoth m', True, 5.4]
['akilan', 'abcd', 'dhanush', 1234, 'vinoth m', True, 5.4]

Nested list:

q = [90,87,65,67,89]
h = [96,97,95,69,99]
a = [99,98,100,76,49]

marks = [q,h,a]
print(marks)

Output:
[[90, 87, 65, 67, 89], [96, 97, 95, 69, 99], [99, 98, 100, 76, 49]]

Extend():
-> The extend() method is used to add all elements from another iterable to the end of a list.
-> It updates the original list by adding each element one by one.

l2 = []
l2.extend('pqrs')
print(l2)

Output:
['p', 'q', 'r', 's']

Append VS Insert VS Extend:

PYTHON - LIST

Keerti Sadana S — Mon, 21 Sep 2026 15:49:28 +0000

-> A list is a built-in data structure used to store an ordered collection of items.
-> They are dynamic, resizable and capable of storing multiple data types.
-> Lists are mutable in Python.
-> This means that once a list is created, we can modify it by adding, removing or changing elements without creating a new list.
-> A list is an index-based data structure.

1) Can we have duplicates objects/elements in a list?
Yes, we can.
Eg: grocery_list = ['soap', 12, 'soap', True, 'rice', 'veggies',4.5]

Sample Program:

name = 'muthu'
name = 'M' + name[1:]
print(name)

Output:
Muthu

Example for Mutablity:

grocery_list = ['soap', 12, True, 'rice', 'veggies',4.5]
grocery_list[0] = 'shampoo'
print(grocery_list)

Output:
['shampoo', 12, True, 'rice', 'veggies', 4.5]

List Properties:
1) A list is a group of individual elements in a single entity
2) In a list, Insertion order is maintained.
3) List is Index / Subscript based.
4) Heterogeneous elements are permitted in a list
5) List Elements are Mutable.

PYTHON - STRING MANIPULATION 2

Keerti Sadana S — Fri, 18 Sep 2026 17:51:19 +0000

Anagram

word1 = input('Enter word: ')
word2 = input('Enter word: ')
if len(word1) != len(word1):
    print('Not Anagram')
else:
    for letter in word1:
        if word1.count(letter) != word2.count(letter):
            print('Not Anagram')
            break
    else:
        print('Anagram')

Output:
Enter word: cat
Enter word: act
Anagram

Rotation:

word = 'abcd' 
for i in range(len(word)):
    rotate = word[1:]+word[0]
    word = rotate
    print(rotate)

Output:
bcda
cdab
dabc
abcd

PYTHON - PASSWORD VALIDATOR AND GENERATOR

Keerti Sadana S — Fri, 18 Sep 2026 17:20:50 +0000

Password Validator:

password = input('Enter Password: ')
if (len(password)<8):
    print('Password should contain at least 8 letters')
elif not any(i.isupper() for i in password):
    print('Password should contain at least 1 uppercase')
elif not any(i.islower() for i in password):
    print('Password should contain at least 1 lowercase')
elif not any(i.isdigit() for i in password):
    print('Password should contain at least 1 digit')
elif not any(not i.isalnum() for i in password):
    print('Password should contain at least 1 special character')
else:
    print('Valid Password')

Output:
Enter Password: Ammu@298
Valid Password

Enter Password: Ammu2345
Password should contain at least 1 special character

Password Generator:

from random import choice
from string import ascii_lowercase,ascii_uppercase,digits
len = int(input('Enter Password Length: '))
letters = ascii_lowercase+ascii_uppercase+digits
password = ''
for i in range(len):
    password += choice(letters)
print(password)

Output:
Enter Password Length: 5
rBMtk