Negative indexing in sequence data structures represents a formal mechanism for accessing elements relative to the end of a linear ordered collection, defined by an integer offset where zero corresponds to the final element and negative values traverse backward to the origin. This operation relies on the mathematical equivalence between a negative index $i$ and a positive index $n + i$, where $n$ is the total length of the sequence, establishing a bijective mapping within the domain of computer science data structures. As a fundamental method of memory addressing abstraction, it serves as a canonical instance of offset-based retrieval in array-like structures, distinct from forward positive indexing yet strictly bound by sequence length constraints.
The core theoretical principle governing strings within Python is their classification as a sequence type characterized by zero-based indexing and negative index access for boundary retrieval. This d…