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How does NumPy handle advanced indexing vs basic slicing internally?

Updated May 17, 2026

Short answer

Basic slicing returns views, while advanced indexing returns copies due to non-contiguous memory access.

Deep explanation

Basic slicing modifies stride metadata, enabling zero-copy views. Advanced indexing (fancy indexing) uses arrays or boolean masks, which require gathering scattered memory locations into a new contiguous buffer. This breaks view semantics and forces allocation of new memory.

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