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We can replace elements in Python lists in many ways. We can use Python list element indexing, for loops, map functions, and list comprehensions.

This article will discuss the above methods to find and replace elements in Python lists.

Searching and replacing Python list elements using list indexing

Let's take the following list as an example and 0change the element at index from 5 to 20.

my_list = [5, 10, 7, 5, 6, 8, 5, 15]

We will 0change the element at index from 5 to 20.

The sample code is as follows.

my_list = [5, 10, 7, 5, 6, 8, 5, 15]
my_list[0] = 20

print(my_list)

Output:

[20, 10, 7, 5, 6, 8, 5, 15]

forFind and replace elements in a Python list using loop method

We use the function in this method enumerate(). It returns an enumeration object which also contains the counter and the element. When we combine enumerate()the function with the loop, it iterates over the object and gets the index along with the element.forenumerate

The code is

my_list = [5, 10, 7, 5, 6, 8, 5, 15]
for index, value in enumerate(my_list):
    if value == 5:
        my_list[index] = 9

print(my_list)

Output:

[9, 10, 7, 9, 6, 8, 9, 15]

Find and Replace Python List Elements Using List Comprehensions

In this method, we can generate a new list by applying pre-defined conditions on the old list.

The syntax is:

my_list = [5, 10, 7, 5, 6, 8, 5, 15]

[9 if value == 5 else value for value in my_list]

print(my_list)

Output:

[9, 10, 7, 9, 6, 8, 9, 15]

mapFind and replace elements in a Python list using the

This method changes the element of the second list item by the index of the first list item.

The code is:

list_1 = [5, 10, 7]
list_2 = [7, 10, 7, 5, 7, 5, 10]

ent = {k: i for i, k in enumerate(list_1)}
result = list(map(ent.get, list_2))

print("list2 after replacement is:", result)

Output:

list2 after replacement is: [2, 1, 2, 0, 2, 0, 1]

in conclusion

1. List indexing is good when we want to replace an element in a list.
2. When we want to replace multiple elements in a list based on a selectivity criterion, list comprehensions are the right choice.
3. The use of round-robin is discouraged as it requires more execution time and memory.