List in python

List

• Lists are used to store multiple items in a single variable.
• Lists are created using square brackets.
• 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.

Ex:

a = [1, 2, 3]
print(a)

b = ["apple", "banana"]
print(b)

List Items - Data Types

• List items can be of any data type.
• A list with strings, integers and boolean values.

Ex:

list1 = ["apple", 1 , False]
list2 = [1, 5, 7, 9, 3]
list3 = [True, False, False]

print(list1)
print(list2)
print(list3)

List Operations:

There are several kinds of list operations,they are:

1. Add()
2. Delete()
3. Reorder()

Add():

• append() → Adds an item at the end.
• insert() → Adds an item at a specific position.
• extend() → Adds multiple items from another list.

Delete():

• pop() → Removes item by index (default: last item).
• remove() → Removes item by value.
• clear() → Removes all items.

Reorder():

• sort() → Sorts items in ascending order.
• reverse() → Reverses the order of items.

Practice problems:

1. Input: [56, 54, 100, 35, 83, 81, 100, 66, 93, 81, 79, 67, 100, 50, 74, 59, 100, 61, 37, 60]
2. Given math scores, find how many scored centum: 100
3. Given scores, grade each score: A > 90, B > 80, C > 60, others D
4. Given scores, count students for each grade

input = [56, 54, 100, 35, 83, 81, 100, 66, 93, 81, 79, 67, 100, 50, 74, 59, 100, 61, 37, 60]
count = 0
for i in input:
    if i == 100:
        count = count + 1
print("Centum scored: ", count)


grade_A = 0
grade_B = 0
grade_C = 0
grade_D = 0

for i in input:
    if i > 90:
        grade_A = grade_A + 1
    elif i > 80:
        grade_B = grade_B + 1
    elif i > 60:
        grade_C = grade_C + 1
    else:
        grade_D = grade_D + 1

print("A_Grade: ", grade_A)
print("B_Grade: ", grade_B)
print("C_Grade: ", grade_C)
print("D_Grade: ", grade_D)

1. Given numbers, reverse numbers [1, 2, 3] -> [3, 2, 1]

num = [1, 2, 3]
num.reverse()
print("Reversed numbers: ", num)

1. Given numbers, rotate them in place N times [1, 2, 3, 4, 5] -> [4, 5, 1, 2, 3]

nums = [1, 2, 3, 4, 5]
N = 2

for i in range(N):
    last = nums.pop()
    nums.insert(0, last)   

print("Rotated list:", nums)

1. Given numbers, double them in place [1, 2, 3, 4, 5] -> [2, 4, 6, 8, 10]

num = [1, 2, 3, 4, 5]
for i in range(len(num)):
    num[i] = num[i] * 2
print("Doubled numbers: ", num)

1. Sort given numbers

num = [1, 2, 3, 4, 5]
num.sort()
print("Sorted numbers: ", num)

1. Sum of given numbers

num = [1, 2, 3, 4, 5]
total = 0
for i in num:
    total = total + i
print("Sum of numbers: ", total)

1. Find even, odd

input = [56, 54, 100, 35, 83, 81, 100]

for i in input:
    if i % 2 == 0:
        print(i, "is even")
    else:
        print(i, "is odd")

1. Multiply by 2

num = [1, 2, 3, 4, 5]
for i in range(len(num)):
    num[i] = num[i] * 2
print("Multiplied by 2: ", num)

1. Compare two lists for equality

list1 = [1, 2, 3]
list2 = [4, 5, 6]
if list1 == list2:
    print("Lists are equal")
else:
    print("Lists are not equal")