1. You have given a Python list. Write a program to find value 20 in the list, and if it is present, replace it with 200. Only update the first occurrence of an item.

    Given input : list1 = [5, 10, 15, 20, 25, 50, 20]

    Expected output: [5, 10, 15, 200, 25, 50, 20]

In [13]:
list1 = [5,10,15,20,25,50,20]

index_20 = list1.index(20)
list1[index_20] = 200

print(list1)

[5, 10, 15, 200, 25, 50, 20]

  1. Given a Python list, write a program to remove all occurrences of item 20.

    Given input : list1 = [5, 20, 15, 20, 25, 50, 20]

    Expected output:[5, 15, 25, 50]

In [22]:
list1 = [5,20,15,20,25,50,20]

for n in range(len(list1)):
    if 20 in list1:
        list1.remove(20)

print(list1)

[5, 15, 25, 50]

  1. Given a two Python list. Write a program to iterate both lists simultaneously and display items from list1 in original order and items from list2 in reverse order.

    Given input :

    list1 = [10, 20, 30, 40]

    list2 = [100, 200, 300, 400]

    Expected output: 10 400 20 300 30 200 40 100

In [33]:
list1 = [10,20,30,40]
list2 = [100,200,300,400]
list3 = []
list3 = list2[::-1]

for (m,n) in zip(list1,list3):
    print(m,n)

10 400
20 300
30 200
40 100