DOC: Document and annotate Index.reindex (#40328). (#44037)

Author: ShivnarenSrinivasan

pandas/core/indexes/base.py

@@ -3963,13 +3963,56 @@ def reindex(
         Parameters
         ----------
         target : an iterable
+        method : {None, 'pad'/'ffill', 'backfill'/'bfill', 'nearest'}, optional
+            * default: exact matches only.
+            * pad / ffill: find the PREVIOUS index value if no exact match.
+            * backfill / bfill: use NEXT index value if no exact match
+            * nearest: use the NEAREST index value if no exact match. Tied
+              distances are broken by preferring the larger index value.
+        level : int, optional
+            Level of multiindex.
+        limit : int, optional
+            Maximum number of consecutive labels in ``target`` to match for
+            inexact matches.
+        tolerance : int or float, optional
+            Maximum distance between original and new labels for inexact
+            matches. The values of the index at the matching locations must
+            satisfy the equation ``abs(index[indexer] - target) <= tolerance``.
+
+            Tolerance may be a scalar value, which applies the same tolerance
+            to all values, or list-like, which applies variable tolerance per
+            element. List-like includes list, tuple, array, Series, and must be
+            the same size as the index and its dtype must exactly match the
+            index's type.
 
         Returns
         -------
         new_index : pd.Index
             Resulting index.
         indexer : np.ndarray[np.intp] or None
             Indices of output values in original index.
+
+        Raises
+        ------
+        TypeError
+            If ``method`` passed along with ``level``.
+        ValueError
+            If non-unique multi-index
+        ValueError
+            If non-unique index and ``method`` or ``limit`` passed.
+
+        See Also
+        --------
+        Series.reindex
+        DataFrame.reindex
+
+        Examples
+        --------
+        >>> idx = pd.Index(['car', 'bike', 'train', 'tractor'])
+        >>> idx
+        Index(['car', 'bike', 'train', 'tractor'], dtype='object')
+        >>> idx.reindex(['car', 'bike'])
+        (Index(['car', 'bike'], dtype='object'), array([0, 1]))
         """
         # GH6552: preserve names when reindexing to non-named target
         # (i.e. neither Index nor Series).