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Practice

Comparing List Concatenation and Element Addition in Python

When working with lists, the concatenation operator (+) and element addition (append, insert) function differently.

The concatenation operation creates a new list, while element addition directly modifies the existing list by appending the new elements.


Concatenation Operation Creating a New List​

The list concatenation operator (+) is used to combine two or more lists into a single new list, without altering the original lists.

List Concatenation Operator Example
list1 = [1, 2, 3]

list2 = [4, 5, 6]

combined_list = list1 + list2

# [1, 2, 3, 4, 5, 6]
print("combined_list:", combined_list)

# [1, 2, 3]
print("list1:", list1)

In the code above, when list1 and list2 are concatenated to create combined_list, list1 and list2 remain unchanged.


Element Addition​

The append() and insert() methods add new elements to an existing list.

These methods directly modify the original list, without creating a new one.

Element Addition Methods Example
list1 = [1, 2, 3]

list1.append(4)
print("list1:", list1)
# [1, 2, 3, 4]

list1.insert(2, "new element")
print("list1:", list1)
# [1, 2, "new element", 3, 4]

In the code above, using the append() and insert() methods to add elements to list1 results in a direct modification of list1.

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