How do Negative List Indices Work in Python?

Understanding Negative List Indices

The given code snippet features a list n of nodes, where link() establishes a connection between the first and last elements. A key component of the code is the use of -1 as an index for the list.

Positive and Negative Indexing

In Python, lists can be indexed both positively and negatively. Positive indices start from 0 and increment to access elements from the left side of the list. Conversely, negative indices start from -1 and decrement to access elements from the right side of the list.

Using Negative Index -1

In the case of list n, list[-1] refers to the last element of the list. This is because negative indices decrement from -1, starting from the right-most element. Therefore, list[-1] accesses the last element, list[-2] accesses the second-last element, and so on.

Example

Consider the list [1, 2, 3, 4, 5].

• list[0] → 1 (first element)
• list[1] → 2 (second element)
• list[-1] → 5 (last element)
• list[-2] → 4 (second-last element)

Conclusion

Negative indices provide a convenient way to access elements from the right side of a list, making it easy to perform operations on the last or penultimate elements.

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