Day - List Functions

extend() vs append() vs insert():

extend()-Adds all elements from an iterable (e.g., list, tuple) to the end of the list.
append()-Adds a single element to the end of the list.
insert()-Inserts a single element at a specified index in the list.

Example for extend():

l1 = [10,20,30]
l2 = [40,50,60]
l1.extend(l2)
print(l1)
print(len(l1))

[10, 20, 30, 40, 50, 60]
6

Example for append():

l1 = [10,20,30]
l2 = [40,50,60]
l1.append(l2)
print(l1)
print(len(l1))

[10, 20, 30, [40, 50, 60]]
4

append() vs extend():

l1 = [10,20,30]
l1.append('abcd')
print(l1)
l1.extend('pqrs')
print(l1)

[10, 20, 30, 'abcd']
[10, 20, 30, 'abcd', 'p', 'q', 'r', 's']

reverse():

The reverse() method in Python is used to reverse the order of the elements in a list in place.

l1 = [10,20,30]
l1.reverse()
print(l1)

[30, 20, 10]

sort():

The sort() method in Python is used to sort the elements of a list in place. It arranges the elements in ascending order by default.

l1 = [10,200,30]
l1.sort()
print(l1)

l1.sort(reverse=True)
print(l1)

[10, 30, 200]
[200, 30, 10]

sorted():

The sorted() function in Python is similar to the sort() method, but with key differences. It returns a new sorted list without modifying the original list.

my_list = [3, 1, 4, 5, 2]
sorted_list = sorted(my_list)
print(sorted_list) 
print(my_list) 

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

min(): To find minimum value in given input.
max(): To find maximum value in given input.
sum(): To find sum of all values in given input.

l1 = [10,200,30,40,50]
print(min(l1))
print(max(l1))
print(sum(l1))

10
200
330

inf(Infinity):

float('inf'):Used to find maximum number.
-float('inf'):Used to find minimum number.

1. Find second minimum value in given input.

l1 = [10,20,310,40,50]
min_value = float('inf')  
second_min = float('inf')  

i = 0
while i <len(l1):
    if l1[i]<min_value: 
        second_min = min_value
        min_value = l1[i] 
    elif l1[i]<second_min:
        second_min = l1[i]
    i+=1
else:
    print(second_min)

20

2. Find second maximum value in given input.

l1 = [10,20,30,40,50]
max_value = -float('inf')  
second_max = -float('inf') 

i = 0
while i <len(l1):
    if l1[i]>max_value: 
        second_max = max_value
        max_value = l1[i] 
    elif l1[i]>second_max:
        second_max = l1[i]
    i+=1
else:
    print(second_max)

40

Bubble sort:

It compares adjacent elements, and swaps them if they are in the wrong order.

Example:1

l1 = [40,30,20,10]
i = 0 
while i<len(l1)-1:
    if l1[i]>l1[i+1]:
        l1[i], l1[i+1] = l1[i+1], l1[i]
    i+=1
print(l1)
i = 0 
while i<len(l1)-2:
    if l1[i]>l1[i+1]:
        l1[i], l1[i+1] = l1[i+1], l1[i]
    i+=1
print(l1)

[30, 20, 10, 40]
[20, 10, 30, 40]

Example:2(using double sort change given list in ascending order and find Kth highest value in a given list)

l1 = [40,30,20,10]

#kth highest value in a given list
j = 1
while j<=len(l1):
    i = 0 
    while i<len(l1)-j:
        if l1[i]>l1[i+1]:
            l1[i], l1[i+1] = l1[i+1], l1[i]
        i+=1
    j+=1
print(l1)
print(l1[-3])

[10, 20, 30, 40]
20

in and not in operators:

Python’s in and not in operators allow you to quickly determine if a given value is or isn’t part of a collection of values.

l1 = [100,67,54,101,220, 670,45, 32]
print(100 in l1)
print(100 not in l1)
print(120 in l1)
print(120 not in l1)

True
False
False
True

Reversing a string:

s = "today is thursday"
reverse = ""
i = 0

while i<len(s):
    reverse = reverse + s[-(i+1)]
    i+=1

print(reverse)

yadsruht si yadot

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