pandas.Index.union¶

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.

Changed in version 0.25.0.

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.

Returns

unionIndex

Examples

Union matching dtypes

>>> idx1 = pd.Index([1, 2, 3, 4])
>>> idx2 = pd.Index([3, 4, 5, 6])
>>> idx1.union(idx2)
Int64Index([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')],
   )

pandas.Index.transpose

pandas.Index.unique