In [ ]:
#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 

given_list = [5, 10, 15, 20, 25, 50, 20]
index20 = given_list.index(20) 
given_list[3] = 200
print(given_list)

[5, 10, 15, 200, 25, 50, 20]
In [ ]:
# Given a Python list, write a program to remove all occurrences of item 20.

list2 = [5, 20, 15, 20, 25, 50, 20]
remove_value = 20
 
list2 = [i for i in list2 if i != remove_value]
print(list2)

[5, 15, 25, 50]
In [ ]:
#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.

listA = [10, 20, 30, 40]
listB = [100, 200, 300, 400]

for x, y in zip(listA, listB[::-1]):
    print(x, y)

10 400
20 300
30 200
40 100