Indexing and selecting data

Use .loc for label-based indexing and .iloc for integer position-based access, as direct operator usage limits optimization in production code. .loc raises KeyError for missing items, supporting labels, label slices (inclusive endpoints), boolean arrays, callables, and tuples. Treat numeric labels like 5 strictly as index labels, not positions. .iloc raises IndexError for out-of-bounds positions but permits out-of-bounds slices. It accepts integers, integer lists, integer slices, boolean arrays, callables, and tuples. Both .loc and .iloc accept callable indexers. Note that destructuring tuple keys into row and column indexes happens before callable application, preventing callables from returning tuples for multi-axis indexing. Omitted axes default to the null slice; for example, p.loc['a'] is equivalent to p.loc['a', :]. For advanced strategies, consult MultiIndex and cookbook documentation. Scope: pandas. Reviewed October 4, 2026.