BUG: pd.read_json May Not Maintain Numeric String Index

Author: theoniko

pandas/io/json/_json.py

@@ -850,6 +850,26 @@ def _convert_axes(self):
         obj = self.obj
         assert obj is not None  # for mypy
         for axis_name in obj._AXIS_ORDERS:
+            if (
+                self.orient == "split"
+                and axis_name == "index"
+                and obj._get_axis(axis_name).dtype == "object"
+                and obj.index.inferred_type == "string"
+            ):
+                index_list = list(obj._get_axis(axis_name).values)
+                are_all_strings = all(type(element) == str for element in index_list)
+                are_int_or_floats = [
+                    True
+                    for element in index_list
+                    if isinstance(element, int) or isinstance(element, float)
+                ]
+                are_all_int_or_floats = all(
+                    are_int_or_floats for element in are_int_or_floats
+                )
+                if are_all_int_or_floats and are_all_strings:
+                    setattr(self.obj, axis_name, obj._get_axis(axis_name))
+                    continue
+
             new_axis, result = self._try_convert_data(
                 name=axis_name,
                 data=obj._get_axis(axis_name),

pandas/tests/io/json/test_pandas.py

@@ -192,11 +192,14 @@ def test_roundtrip_str_axes(self, orient, convert_axes, numpy, dtype):
         # to disambiguate whether those keys actually were strings or numeric
         # beforehand and numeric wins out.
         # TODO: Split should be able to support this
-        if convert_axes and (orient in ("split", "index", "columns")):
+        if convert_axes and (orient in ("index", "columns")):
             expected.columns = expected.columns.astype(np.int64)
             expected.index = expected.index.astype(np.int64)
         elif orient == "records" and convert_axes:
             expected.columns = expected.columns.astype(np.int64)
+        elif convert_axes and orient == "split":
+            expected.columns = expected.columns.astype(np.int64)
+            expected.index = expected.index.astype(str)
 
         assert_json_roundtrip_equal(result, expected, orient)