Adding to a list in python with makes a new list with different id

When working with lists in Python, it is important to understand how adding elements to a list affects its identity. In some cases, adding elements to a list can create a new list with a different id. In this article, we will explore three different ways to add elements to a list in Python and discuss which option is better.

Option 1: Using the append() method

The append() method is a built-in function in Python that allows us to add elements to the end of a list. Let’s see an example:

my_list = [1, 2, 3]
my_list.append(4)
print(my_list)  # Output: [1, 2, 3, 4]

Using the append() method modifies the original list in-place, meaning it does not create a new list with a different id. This can be useful when you want to add elements to an existing list without creating a new list object.

Option 2: Using the + operator

The + operator can be used to concatenate two lists together. Let’s see an example:

my_list = [1, 2, 3]
new_list = my_list + [4]
print(new_list)  # Output: [1, 2, 3, 4]

Using the + operator creates a new list with a different id. This means that the original list remains unchanged, and a new list object is created with the concatenated elements. This can be useful when you want to create a new list without modifying the original list.

Option 3: Using list comprehension

List comprehension is a concise way to create lists in Python. It allows you to iterate over an iterable and apply an expression or condition to each element. Let’s see an example:

my_list = [1, 2, 3]
new_list = [x for x in my_list] + [4]
print(new_list)  # Output: [1, 2, 3, 4]

Using list comprehension creates a new list with a different id. Similar to the + operator, the original list remains unchanged, and a new list object is created with the desired elements. List comprehension can be useful when you want to apply a transformation or condition to the elements before adding them to the new list.

After exploring these three options, it is clear that the best option depends on the specific use case. If you want to add elements to an existing list without creating a new list object, using the append() method is the most efficient choice. However, if you want to create a new list without modifying the original list, using the + operator or list comprehension are both viable options.

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