Fix bug when index type casting in read_json table (pandas-dev#25433)

doc/source/whatsnew/v0.25.0.rst

@@ -194,6 +194,7 @@ I/O
 
 - Fixed bug in missing text when using :meth:`to_clipboard` if copying utf-16 characters in Python 3 on Windows (:issue:`25040`)
 - Bug in :func:`read_json` for ``orient='table'`` when it tries to infer dtypes by default, which is not applicable as dtypes are already defined in the JSON schema (:issue:`21345`)
+- Bug in :func:`read_json` for ``orient='table'`` and float index, as it infers index dtype by default, which is not applicable because index dtype is already defined in the JSON schema (:issue:`25433`)
 -
 -
 -

pandas/io/json/json.py

@@ -227,7 +227,7 @@ def _write(self, obj, orient, double_precision, ensure_ascii,
 
 
 def read_json(path_or_buf=None, orient=None, typ='frame', dtype=None,
-              convert_axes=True, convert_dates=True, keep_default_dates=True,
+              convert_axes=None, convert_dates=True, keep_default_dates=True,
               numpy=False, precise_float=False, date_unit=None, encoding=None,
               lines=False, chunksize=None, compression='infer'):
     """
@@ -289,6 +289,13 @@ def read_json(path_or_buf=None, orient=None, typ='frame', dtype=None,
 
     convert_axes : boolean, default True
         Try to convert the axes to the proper dtypes.
+
+        Not applicable with ``orient='table'``.
+
+        .. versionchanged:: 0.25
+
+           Not applicable with ``orient='table'``.
+
     convert_dates : boolean, default True
         List of columns to parse for dates; If True, then try to parse
         datelike columns default is True; a column label is datelike if
@@ -417,8 +424,12 @@ def read_json(path_or_buf=None, orient=None, typ='frame', dtype=None,
 
     if orient == 'table' and dtype:
         raise ValueError("cannot pass both dtype and orient='table'")
+    if orient == 'table' and convert_axes:
+        raise ValueError("cannot pass both convert_axes and orient='table'")
 
     dtype = orient != 'table' if dtype is None else dtype
+    if convert_axes is None:
+        convert_axes = orient != 'table'
 
     compression = _infer_compression(path_or_buf, compression)
     filepath_or_buffer, _, compression, should_close = get_filepath_or_buffer(

pandas/tests/io/json/test_pandas.py

@@ -1202,6 +1202,14 @@ def test_data_frame_size_after_to_json(self):
 
         assert size_before == size_after
 
+    @pytest.mark.parametrize('index', [None, [1., 2.], ['1', '2'],
+                                       ['1.', '2.']])
+    def test_from_json_to_json_table_index(self, index):
+        expected = DataFrame({'a': [1, 2]}, index=index)
+        dfjson = expected.to_json(orient='table')
+        result = pd.read_json(dfjson, orient='table')
+        assert_frame_equal(result, expected)
+
     def test_from_json_to_json_table_dtypes(self):
         # GH21345
         expected = pd.DataFrame({'a': [1, 2], 'b': [3., 4.], 'c': ['5', '6']})