pandas.Index.union — pandas 2.2.3 documentation (original) (raw)

final Index.union(other, sort=None)[source]#

Form the union of two Index objects.

If the Index objects are incompatible, both Index objects will be cast to dtype(‘object’) first.

Parameters:

otherIndex or array-like

sortbool or None, default None

Whether to sort the resulting Index.

• None : Sort the result, except when
  1. self and other are equal.
  2. self or other has length 0.
  3. Some values in self or other cannot be compared. A RuntimeWarning is issued in this case.
• False : do not sort the result.
• True : Sort the result (which may raise TypeError).

Returns:

Index

Examples

Union matching dtypes

idx1 = pd.Index([1, 2, 3, 4]) idx2 = pd.Index([3, 4, 5, 6]) idx1.union(idx2) Index([1, 2, 3, 4, 5, 6], dtype='int64')

Union mismatched dtypes

idx1 = pd.Index(['a', 'b', 'c', 'd']) idx2 = pd.Index([1, 2, 3, 4]) idx1.union(idx2) Index(['a', 'b', 'c', 'd', 1, 2, 3, 4], dtype='object')

MultiIndex case

idx1 = pd.MultiIndex.from_arrays( ... [[1, 1, 2, 2], ["Red", "Blue", "Red", "Blue"]] ... ) idx1 MultiIndex([(1, 'Red'), (1, 'Blue'), (2, 'Red'), (2, 'Blue')], ) idx2 = pd.MultiIndex.from_arrays( ... [[3, 3, 2, 2], ["Red", "Green", "Red", "Green"]] ... ) idx2 MultiIndex([(3, 'Red'), (3, 'Green'), (2, 'Red'), (2, 'Green')], ) idx1.union(idx2) MultiIndex([(1, 'Blue'), (1, 'Red'), (2, 'Blue'), (2, 'Green'), (2, 'Red'), (3, 'Green'), (3, 'Red')], ) idx1.union(idx2, sort=False) MultiIndex([(1, 'Red'), (1, 'Blue'), (2, 'Red'), (2, 'Blue'), (3, 'Red'), (3, 'Green'), (2, 'Green')], )