diff --git a/doc/source/whatsnew/v1.1.0.rst b/doc/source/whatsnew/v1.1.0.rst
index 9bd4ddbb624d9..0b2493cfaf7ff 100644
--- a/doc/source/whatsnew/v1.1.0.rst
+++ b/doc/source/whatsnew/v1.1.0.rst
@@ -1112,6 +1112,7 @@ Reshaping
- Fixed bug in :func:`melt` where melting MultiIndex columns with ``col_level`` > 0 would raise a ``KeyError`` on ``id_vars`` (:issue:`34129`)
- Bug in :meth:`Series.where` with an empty Series and empty ``cond`` having non-bool dtype (:issue:`34592`)
- Fixed regression where :meth:`DataFrame.apply` would raise ``ValueError`` for elements whth ``S`` dtype (:issue:`34529`)
+- Bug in :meth:`DataFrame.append` leading to sorting columns even when ``sort=False`` is specified (:issue:`35092`)
Sparse
^^^^^^
diff --git a/pandas/core/indexes/api.py b/pandas/core/indexes/api.py
index 4c5a70f4088ee..9849742abcfca 100644
--- a/pandas/core/indexes/api.py
+++ b/pandas/core/indexes/api.py
@@ -214,7 +214,13 @@ def conv(i):
return result.union_many(indexes[1:])
else:
for other in indexes[1:]:
- result = result.union(other)
+ # GH 35092. Index.union expects sort=None instead of sort=True
+ # to signify that sort=True isn't fully implemented and
+ # legacy implementation sometimes might not sort (see GH 24959)
+ # In this case we currently sort in _get_combined_index
+ if sort:
+ sort = None
+ result = result.union(other, sort=sort)
return result
elif kind == "array":
index = indexes[0]
diff --git a/pandas/tests/frame/test_constructors.py b/pandas/tests/frame/test_constructors.py
index dba243f1a339a..ab4f7781467e7 100644
--- a/pandas/tests/frame/test_constructors.py
+++ b/pandas/tests/frame/test_constructors.py
@@ -2542,11 +2542,13 @@ def test_construct_with_two_categoricalindex_series(self):
index=pd.CategoricalIndex(["f", "female", "m", "male", "unknown"]),
)
result = DataFrame([s1, s2])
+ # GH 35092. Extra s2 columns are now appended to s1 columns
+ # in original order
expected = DataFrame(
np.array(
- [[np.nan, 39.0, np.nan, 6.0, 4.0], [2.0, 152.0, 2.0, 242.0, 150.0]]
+ [[39.0, 6.0, 4.0, np.nan, np.nan], [152.0, 242.0, 150.0, 2.0, 2.0]]
),
- columns=["f", "female", "m", "male", "unknown"],
+ columns=["female", "male", "unknown", "f", "m"],
)
tm.assert_frame_equal(result, expected)
diff --git a/pandas/tests/indexes/test_common.py b/pandas/tests/indexes/test_common.py
index 02a173eb4958d..c85696e02ad39 100644
--- a/pandas/tests/indexes/test_common.py
+++ b/pandas/tests/indexes/test_common.py
@@ -13,8 +13,9 @@
from pandas.core.dtypes.common import is_period_dtype, needs_i8_conversion
import pandas as pd
-from pandas import CategoricalIndex, MultiIndex, RangeIndex
+from pandas import CategoricalIndex, Index, MultiIndex, RangeIndex
import pandas._testing as tm
+from pandas.core.indexes.api import union_indexes
class TestCommon:
@@ -395,3 +396,18 @@ def test_astype_preserves_name(self, index, dtype, copy):
assert result.names == index.names
else:
assert result.name == index.name
+
+
+@pytest.mark.parametrize("arr", [[0, 1, 4, 3]])
+@pytest.mark.parametrize("dtype", ["int8", "int16", "int32", "int64"])
+def test_union_index_no_sort(arr, sort, dtype):
+ # GH 35092. Check that we don't sort with sort=False
+ ind1 = Index(arr[:2], dtype=dtype)
+ ind2 = Index(arr[2:], dtype=dtype)
+
+ # sort is None indicates that we sort the combined index
+ if sort is None:
+ arr.sort()
+ expected = Index(arr, dtype=dtype)
+ result = union_indexes([ind1, ind2], sort=sort)
+ tm.assert_index_equal(result, expected)
diff --git a/pandas/tests/reshape/test_concat.py b/pandas/tests/reshape/test_concat.py
index ffeb5ff0f8aaa..ff95d8ad997a4 100644
--- a/pandas/tests/reshape/test_concat.py
+++ b/pandas/tests/reshape/test_concat.py
@@ -2857,3 +2857,17 @@ def test_concat_frame_axis0_extension_dtypes():
result = pd.concat([df2, df1], ignore_index=True)
expected = pd.DataFrame({"a": [4, 5, 6, 1, 2, 3]}, dtype="Int64")
tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize("sort", [True, False])
+def test_append_sort(sort):
+ # GH 35092. Check that DataFrame.append respects the sort argument.
+ df1 = pd.DataFrame(data={0: [1, 2], 1: [3, 4]})
+ df2 = pd.DataFrame(data={3: [1, 2], 2: [3, 4]})
+ cols = list(df1.columns) + list(df2.columns)
+ if sort:
+ cols.sort()
+
+ result = df1.append(df2, sort=sort).columns
+ expected = type(result)(cols)
+ tm.assert_index_equal(result, expected)
diff --git a/pandas/tests/reshape/test_melt.py b/pandas/tests/reshape/test_melt.py
index a0fa10802f860..03fda038539e2 100644
--- a/pandas/tests/reshape/test_melt.py
+++ b/pandas/tests/reshape/test_melt.py
@@ -691,11 +691,11 @@ def test_unbalanced(self):
)
df["id"] = df.index
exp_data = {
- "X": ["X1", "X1", "X2", "X2"],
- "A": [1.0, 3.0, 2.0, 4.0],
- "B": [5.0, np.nan, 6.0, np.nan],
- "id": [0, 0, 1, 1],
- "year": [2010, 2011, 2010, 2011],
+ "X": ["X1", "X2", "X1", "X2"],
+ "A": [1.0, 2.0, 3.0, 4.0],
+ "B": [5.0, 6.0, np.nan, np.nan],
+ "id": [0, 1, 0, 1],
+ "year": [2010, 2010, 2011, 2011],
}
expected = pd.DataFrame(exp_data)
expected = expected.set_index(["id", "year"])[["X", "A", "B"]]
@@ -938,10 +938,10 @@ def test_nonnumeric_suffix(self):
)
expected = pd.DataFrame(
{
- "A": ["X1", "X1", "X2", "X2"],
- "colname": ["placebo", "test", "placebo", "test"],
- "result": [5.0, np.nan, 6.0, np.nan],
- "treatment": [1.0, 3.0, 2.0, 4.0],
+ "A": ["X1", "X2", "X1", "X2"],
+ "colname": ["placebo", "placebo", "test", "test"],
+ "result": [5.0, 6.0, np.nan, np.nan],
+ "treatment": [1.0, 2.0, 3.0, 4.0],
}
)
expected = expected.set_index(["A", "colname"])
@@ -985,10 +985,10 @@ def test_float_suffix(self):
)
expected = pd.DataFrame(
{
- "A": ["X1", "X1", "X1", "X1", "X2", "X2", "X2", "X2"],
- "colname": [1, 1.1, 1.2, 2.1, 1, 1.1, 1.2, 2.1],
- "result": [0.0, np.nan, 5.0, np.nan, 9.0, np.nan, 6.0, np.nan],
- "treatment": [np.nan, 1.0, np.nan, 3.0, np.nan, 2.0, np.nan, 4.0],
+ "A": ["X1", "X2", "X1", "X2", "X1", "X2", "X1", "X2"],
+ "colname": [1.2, 1.2, 1.0, 1.0, 1.1, 1.1, 2.1, 2.1],
+ "result": [5.0, 6.0, 0.0, 9.0, np.nan, np.nan, np.nan, np.nan],
+ "treatment": [np.nan, np.nan, np.nan, np.nan, 1.0, 2.0, 3.0, 4.0],
}
)
expected = expected.set_index(["A", "colname"])
diff --git a/pandas/tests/test_strings.py b/pandas/tests/test_strings.py
index d9396d70f9112..3a4e54052305e 100644
--- a/pandas/tests/test_strings.py
+++ b/pandas/tests/test_strings.py
@@ -636,8 +636,15 @@ def test_str_cat_align_mixed_inputs(self, join):
# mixed list of indexed/unindexed
u = np.array(["A", "B", "C", "D"])
expected_outer = Series(["aaA", "bbB", "c-C", "ddD", "-e-"])
+
# joint index of rhs [t, u]; u will be forced have index of s
- rhs_idx = t.index & s.index if join == "inner" else t.index | s.index
+ # GH 35092. If right join, maintain order of t.index
+ if join == "inner":
+ rhs_idx = t.index & s.index
+ elif join == "right":
+ rhs_idx = t.index.union(s.index, sort=False)
+ else:
+ rhs_idx = t.index | s.index
expected = expected_outer.loc[s.index.join(rhs_idx, how=join)]
result = s.str.cat([t, u], join=join, na_rep="-")