Understanding Negative List Indexing in Python

In Python, accessing elements in a list using negative indices can be confusing to some. While a positive index like 0 refers to the first element, a negative index like -1 indicates the last element.

Consider the example code you provided:

# node list
n = []
for i in xrange(1, numnodes   1):
    tmp = session.newobject();
    n.append(tmp)
link(n[0], n[-1])

Here, n[0] represents the first element of the list n, which is the element at the beginning of the list. On the other hand, n[-1] refers to the last element of the list, the element at the far right.

Negative indexing allows you to iterate through a list from the end to the beginning. For example, n[-2] would give you the second-to-last element, and n[-3] would give you the third-to-last element.

Understanding negative indexing is essential for manipulating lists efficiently in Python. It allows you to access and modify elements from both the beginning and end of the list, making it a powerful tool for working with sequences.