What's the Difference Between Python's `append()` and `extend()` List Methods?

Distinguishing Python's Append and Extend List Methods

In Python, the list data structure offers two methods for adding elements: append() and extend(). These methods serve different purposes, and understanding their distinction is crucial for effective list manipulation.

Append: Appending a Single Object

The append() method takes a single argument and adds it to the end of the existing list. This object can be any type, including another list. When an object is appended to a list, it becomes the last element.

For example:

>>> x = [1, 2, 3]
>>> x.append([4, 5])
>>> print(x)
[1, 2, 3, [4, 5]]

In this case, a list containing [4, 5] is appended to the end of the list x, resulting in a list of lists.

Extend: Adding Multiple from an Iterable

Unlike append(), the extend() method takes an iterable (such as a list, tuple, or set) as its argument and extends the existing list with all the elements from that iterable. This allows for convenient addition of multiple objects at once.

Consider the following example:

>>> x = [1, 2, 3]
>>> x.extend([4, 5])
>>> print(x)
[1, 2, 3, 4, 5]

Here, the list [4, 5] is extended into the list x, resulting in a single list with all the elements.

Summary

To summarize, append() adds a single object to the end of a list, while extend() appends multiple objects from an iterable. By understanding this difference, developers can utilize these methods effectively to manipulate lists according to their specific requirements.

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