How to Efficiently Concatenate Lists in Python?

How to Concatenate Lists in Python

Concatenating lists in Python is a common task, and there are several ways to do it. The most popular and straightforward approach is to use the operator.

Using the Operator

The operator is used to add elements to a list, and it can also be used to concatenate two lists. For example:

listone = [1, 2, 3]
listtwo = [4, 5, 6]

joinedlist = listone + listtwo

The result of this operation is a new list called joinedlist, which contains six elements: [1, 2, 3, 4, 5, 6].

Example

Consider the following Python code:

listone = [1, 2, 3]
listtwo = [4, 5, 6]

print(listone)
print(listtwo)

Output:

[1, 2, 3]
[4, 5, 6]

Now, let's concatenate the two lists using the operator and store the result in a new list called joinedlist:

joinedlist = listone + listtwo

print(joinedlist)

Output:

[1, 2, 3, 4, 5, 6]

As you can see, the joinedlist now contains the elements from both listone and listtwo.

Shallow vs. Deep Copy

It's important to note that the operator creates a new list with shallow copies of the items in the original lists. This means that if the original lists are modified, the joined list will not be affected. To create deep copies, which are independent of the original lists, you can use the copy.deepcopy() function from the copy module:

import copy

listone = [1, 2, 3]
listtwo = [4, 5, 6]

joinedlist = copy.deepcopy(listone + listtwo)

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