fix unnecessary sort in pd.read_json and orient="index"

pandas/core/indexes/api.py

@@ -169,7 +169,10 @@ def _union_indexes(indexes, sort=True):
     if len(indexes) == 1:
         result = indexes[0]
         if isinstance(result, list):
-            result = Index(sorted(result))
+            if sort:
+                result = Index(sorted(result))
+            else:
+                result = Index(result)
         return result
 
     indexes, kind = _sanitize_and_check(indexes)

pandas/io/json/_json.py

@@ -12,7 +12,7 @@
 
 from pandas.core.dtypes.common import ensure_str, is_period_dtype
 
-from pandas import DataFrame, MultiIndex, Series, isna, to_datetime
+from pandas import DataFrame, MultiIndex, Series, isna, to_datetime, compat
 from pandas._typing import Scalar
 from pandas.core.reshape.concat import concat
 
@@ -1112,15 +1112,14 @@ def _parse_no_numpy(self):
             self.check_keys_split(decoded)
             self.obj = DataFrame(dtype=None, **decoded)
         elif orient == "index":
-            self.obj = (
-                DataFrame.from_dict(
-                    loads(json, precise_float=self.precise_float),
-                    dtype=None,
-                    orient="index",
-                )
-                .sort_index(axis="columns")
-                .sort_index(axis="index")
+            self.obj = DataFrame.from_dict(
+                loads(json, precise_float=self.precise_float),
+                dtype=None,
+                orient="index",
             )
+            if compat.PY35:
+                self.obj.sort_index(axis="columns", inplace=True)
+                self.obj.sort_index(axis="index", inplace=True)
         elif orient == "table":
             self.obj = parse_table_schema(json, precise_float=self.precise_float)
         else:

pandas/tests/frame/test_alter_axes.py

@@ -667,10 +667,10 @@ def test_rename(self, float_frame):
         # gets sorted alphabetical
         df = DataFrame(data)
         renamed = df.rename(index={"foo": "bar", "bar": "foo"})
-        tm.assert_index_equal(renamed.index, Index(["foo", "bar"]))
+        tm.assert_index_equal(renamed.index, Index(["bar", "foo"]))
 
         renamed = df.rename(index=str.upper)
-        tm.assert_index_equal(renamed.index, Index(["BAR", "FOO"]))
+        tm.assert_index_equal(renamed.index, Index(["FOO", "BAR"]))
 
         # have to pass something
         with pytest.raises(TypeError, match="must pass an index to rename"):

pandas/tests/indexing/multiindex/test_setitem.py

@@ -159,7 +159,7 @@ def test_multiindex_setitem(self):
         )
 
         expected = df_orig.copy()
-        expected.iloc[[0, 2, 3]] *= 2
+        expected.iloc[[0, 1, 3]] *= 2
 
         idx = pd.IndexSlice
         df = df_orig.copy()

pandas/tests/io/json/test_pandas.py

@@ -168,7 +168,7 @@ def test_roundtrip_simple(self, orient, convert_axes, numpy, dtype):
 
         expected = self.frame.copy()
 
-        if not numpy and (orient == "index" or (PY35 and orient == "columns")):
+        if not numpy and (PY35 and (orient == "index" or orient == "columns")):
             # TODO: debug why sort is required
             expected = expected.sort_index()
 
@@ -188,7 +188,7 @@ def test_roundtrip_intframe(self, orient, convert_axes, numpy, dtype):
             data, orient=orient, convert_axes=convert_axes, numpy=numpy, dtype=dtype
         )
         expected = self.intframe.copy()
-        if not numpy and (orient == "index" or (PY35 and orient == "columns")):
+        if not numpy and (PY35 and (orient == "index" or orient == "columns")):
             expected = expected.sort_index()
 
         if orient == "records" or orient == "values":
@@ -228,7 +228,7 @@ def test_roundtrip_str_axes(self, orient, convert_axes, numpy, dtype):
         )
 
         expected = df.copy()
-        if not numpy and (orient == "index" or (PY35 and orient == "columns")):
+        if not numpy and (PY35 and (orient == "index" or orient == "columns")):
             expected = expected.sort_index()
 
         if not dtype: