diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index a995fc10a6674..805cd213f0203 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -2183,7 +2183,7 @@ def _get_consensus_name(self, other):
return self._shallow_copy(name=name)
return self
- def union(self, other):
+ def union(self, other, sort=True):
"""
Form the union of two Index objects and sorts if possible.
@@ -2241,27 +2241,31 @@ def union(self, other):
allow_fill=False)
result = _concat._concat_compat((self._values, other_diff))
- try:
- self._values[0] < other_diff[0]
- except TypeError as e:
- warnings.warn("%s, sort order is undefined for "
- "incomparable objects" % e, RuntimeWarning,
- stacklevel=3)
- else:
- types = frozenset((self.inferred_type,
- other.inferred_type))
- if not types & _unsortable_types:
- result.sort()
+ if sort:
+ try:
+ self._values[0] < other_diff[0]
+ except TypeError as e:
+ warnings.warn("%s, sort order is undefined for "
+ "incomparable objects" % e,
+ RuntimeWarning,
+ stacklevel=3)
+ else:
+ types = frozenset((self.inferred_type,
+ other.inferred_type))
+ if not types & _unsortable_types:
+ result.sort()
else:
result = self._values
- try:
- result = np.sort(result)
- except TypeError as e:
- warnings.warn("%s, sort order is undefined for "
- "incomparable objects" % e, RuntimeWarning,
- stacklevel=3)
+ if sort:
+ try:
+ result = np.sort(result)
+ except TypeError as e:
+ warnings.warn("%s, sort order is undefined for "
+ "incomparable objects" % e,
+ RuntimeWarning,
+ stacklevel=3)
# for subclasses
return self._wrap_union_result(other, result)
@@ -2326,7 +2330,7 @@ def intersection(self, other):
taken.name = None
return taken
- def difference(self, other):
+ def difference(self, other, sort=True):
"""
Return a new Index with elements from the index that are not in
`other`.
@@ -2366,14 +2370,15 @@ def difference(self, other):
label_diff = np.setdiff1d(np.arange(this.size), indexer,
assume_unique=True)
the_diff = this.values.take(label_diff)
- try:
- the_diff = sorting.safe_sort(the_diff)
- except TypeError:
- pass
+ if sort:
+ try:
+ the_diff = sorting.safe_sort(the_diff)
+ except TypeError:
+ pass
return this._shallow_copy(the_diff, name=result_name, freq=None)
- def symmetric_difference(self, other, result_name=None):
+ def symmetric_difference(self, other, result_name=None, sort=True):
"""
Compute the symmetric difference of two Index objects.
It's sorted if sorting is possible.
@@ -2426,10 +2431,11 @@ def symmetric_difference(self, other, result_name=None):
right_diff = other.values.take(right_indexer)
the_diff = _concat._concat_compat([left_diff, right_diff])
- try:
- the_diff = sorting.safe_sort(the_diff)
- except TypeError:
- pass
+ if sort:
+ try:
+ the_diff = sorting.safe_sort(the_diff)
+ except TypeError:
+ pass
attribs = self._get_attributes_dict()
attribs['name'] = result_name
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 307cda7f2d1cb..5835aee9a68b7 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -766,6 +766,103 @@ def test_union(self):
tm.assert_contains_all(self.strIndex, secondCat)
tm.assert_contains_all(self.dateIndex, firstCat)
+ def test_union_sorting_false(self):
+
+ # GH 17839
+ dt_index = pd.DatetimeIndex(["20/12/2012", "15/05/2015",
+ "1/1/2011", "1/7/2017"])
+ first = pd.Index([2, 0, 4, 3])
+ second = pd.Index([1, 4])
+ everything = pd.Index([2, 0, 4, 3, 1])
+ union = first.union(second, sort=False)
+ assert tm.equalContents(union, everything)
+
+ cases = [klass(second.values) for klass in [np.array, Series, list]]
+ for case in cases:
+ result = first.union(case, sort=False)
+ assert tm.equalContents(result, everything)
+
+ # Corner cases
+ union = first.union(first, sort=False)
+ assert union is first
+
+ union = first.union([], sort=False)
+ assert union is first
+
+ union = Index([]).union(first, sort=False)
+ assert union is first
+
+ # preserve names
+ first = Index(list('ba'), name='A')
+ second = Index(list('ba'), name='B')
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name=None)
+ tm.assert_index_equal(union, expected)
+
+ first = Index(list('ba'), name='A')
+ second = Index([], name='B')
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name=None)
+ tm.assert_index_equal(union, expected)
+
+ first = Index([], name='A')
+ second = Index(list('ba'), name='B')
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name=None)
+ tm.assert_index_equal(union, expected)
+
+ first = Index(list('ba'))
+ second = Index(list('ba'), name='B')
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name='B')
+ tm.assert_index_equal(union, expected)
+
+ first = Index([])
+ second = Index(list('ba'), name='B')
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name='B')
+ tm.assert_index_equal(union, expected)
+
+ first = Index(list('ba'))
+ second = Index([], name='B')
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name='B')
+ tm.assert_index_equal(union, expected)
+
+ first = Index(list('ba'), name='A')
+ second = Index(list('ba'))
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name='A')
+ tm.assert_index_equal(union, expected)
+
+ first = Index(list('ba'), name='A')
+ second = Index([])
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name='A')
+ tm.assert_index_equal(union, expected)
+
+ first = Index([], name='A')
+ second = Index(list('ba'))
+ union = first.union(second, sort=False)
+ expected = Index(list('ba'), name='A')
+ tm.assert_index_equal(union, expected)
+
+ first = pd.Index([2, 0, 4, 3])
+ with tm.assert_produces_warning(RuntimeWarning):
+ firstCat = first.union(dt_index, sort=False)
+ secondCat = first.union(first, sort=False)
+
+ if dt_index.dtype == np.object_:
+ appended = np.append(first, dt_index)
+ else:
+ appended = np.append(first, dt_index.astype('O'))
+
+ assert tm.equalContents(firstCat, appended)
+ assert tm.equalContents(secondCat, first)
+ tm.assert_contains_all(first, firstCat)
+ tm.assert_contains_all(first, secondCat)
+ tm.assert_contains_all(dt_index, firstCat)
+
def test_add(self):
idx = self.strIndex
expected = Index(self.strIndex.values * 2)
@@ -896,6 +993,34 @@ def test_difference(self):
assert len(result) == 0
assert result.name == first.name
+ def test_difference_sorting_false(self):
+
+ # GH 17839
+ first = pd.Index([2, 0, 4, 3])
+ second = pd.Index([2, 1])
+ answer = pd.Index([0, 4, 3])
+ first.name = 'name'
+ # different names
+ result = first.difference(second, sort=False)
+
+ assert tm.equalContents(result, answer)
+ assert result.name is None
+
+ # same names
+ second.name = 'name'
+ result = first.difference(second, sort=False)
+ assert result.name == 'name'
+
+ # with empty
+ result = first.difference([], sort=False)
+ assert tm.equalContents(result, first)
+ assert result.name == first.name
+
+ # with everything
+ result = first.difference(first, sort=False)
+ assert len(result) == 0
+ assert result.name == first.name
+
def test_symmetric_difference(self):
# smoke
idx1 = Index([1, 2, 3, 4], name='idx1')
@@ -944,6 +1069,55 @@ def test_symmetric_difference(self):
assert tm.equalContents(result, expected)
assert result.name == 'new_name'
+ def test_symmetric_difference_sorting_false(self):
+
+ # GH 17839
+ # smoke
+ idx1 = Index([1, 2, 3, 4], name='idx1')
+ idx2 = Index([2, 3, 4, 5])
+ result = idx1.symmetric_difference(idx2, sort=False)
+ expected = Index([1, 5])
+ assert tm.equalContents(result, expected)
+ assert result.name is None
+
+ # __xor__ syntax
+ expected = idx1 ^ idx2
+ assert tm.equalContents(result, expected)
+ assert result.name is None
+
+ # multiIndex
+ idx1 = MultiIndex.from_tuples(self.tuples)
+ idx2 = MultiIndex.from_tuples([('foo', 1), ('bar', 3)])
+ result = idx1.symmetric_difference(idx2, sort=False)
+ expected = MultiIndex.from_tuples([('bar', 2), ('baz', 3), ('bar', 3)])
+ assert tm.equalContents(result, expected)
+
+ # nans:
+ idx1 = Index([1, np.nan, 2, 3])
+ idx2 = Index([0, 1, np.nan])
+ idx3 = Index([0, 1])
+
+ result = idx1.symmetric_difference(idx2, sort=False)
+ expected = Index([2.0, 3.0, 0.0])
+ tm.assert_index_equal(result, expected)
+
+ result = idx1.symmetric_difference(idx3, sort=False)
+ expected = Index([np.nan, 2.0, 3.0, 0.0])
+ tm.assert_index_equal(result, expected)
+
+ # other not an Index:
+ idx1 = Index([5, 3, 4, 2], name='idx1')
+ idx2 = np.array([3, 2, 4, 1])
+ expected = Index([5, 1])
+ result = idx1.symmetric_difference(idx2, sort=False)
+ assert tm.equalContents(result, expected)
+ assert result.name == 'idx1'
+
+ result = idx1.symmetric_difference(idx2, result_name='new_name',
+ sort=False)
+ assert tm.equalContents(result, expected)
+ assert result.name == 'new_name'
+
def test_is_numeric(self):
assert not self.dateIndex.is_numeric()
assert not self.strIndex.is_numeric()