ENH: add __fspath__ to pandas own file-like objects

- HDFStore
- ExcelFile

(cherry picked from commit f9baec385e2513234a69a05031d2753899290d38)

Author: TomAugspurger

doc/source/whatsnew/v0.21.0.txt

@@ -20,8 +20,10 @@ Check the :ref:`API Changes <whatsnew_0210.api_breaking>` and :ref:`deprecations
 New features
 ~~~~~~~~~~~~
 
-- Support for `PEP 519 -- Adding a file system path protocol <https://www.python.org/dev/peps/pep-0519/>`_ on most readers and writers (:issue:`13823`)
-
+- Support for `PEP 519 -- Adding a file system path protocol
+  <https://www.python.org/dev/peps/pep-0519/>`_ on most readers and writers (:issue:`13823`)
+- Added `__fspath__` method to :class`:pandas.HDFStore`, :class:`pandas.ExcelFile`,
+  and :class:`pandas.ExcelWriter` to work properly with the file system path protocol (:issue:`13823`)
 
 
 .. _whatsnew_0210.enhancements.other:

pandas/io/excel.py

@@ -263,6 +263,9 @@ def __init__(self, io, **kwds):
             raise ValueError('Must explicitly set engine if not passing in'
                              ' buffer or path for io.')
 
+    def __fspath__(self):
+        return self._io
+
     def parse(self, sheetname=0, header=0, skiprows=None, skip_footer=0,
               names=None, index_col=None, parse_cols=None, parse_dates=False,
               date_parser=None, na_values=None, thousands=None,
@@ -758,6 +761,9 @@ def __init__(self, path, engine=None,
         else:
             self.datetime_format = datetime_format
 
+    def __fspath__(self):
+        return _stringify_path(self.path)
+
     def _get_sheet_name(self, sheet_name):
         if sheet_name is None:
             sheet_name = self.cur_sheet

pandas/io/formats/excel.py

@@ -619,10 +619,10 @@ def write(self, writer, sheet_name='Sheet1', startrow=0,
         from pandas.io.excel import ExcelWriter
         from pandas.io.common import _stringify_path
 
-        writer = _stringify_path(writer)
-        need_save = False
-        if isinstance(writer, string_types):
-            writer = ExcelWriter(writer, engine=engine)
+        if isinstance(writer, ExcelWriter):
+            need_save = False
+        else:
+            writer = ExcelWriter(_stringify_path(writer), engine=engine)
             need_save = True
 
         formatted_cells = self.get_formatted_cells()

pandas/io/pytables.py

@@ -437,7 +437,7 @@ def __init__(self, path, mode=None, complevel=None, complib=None,
                 "complib only supports {libs} compression.".format(
                     libs=tables.filters.all_complibs))
 
-        self._path = path
+        self._path = _stringify_path(path)
         if mode is None:
             mode = 'a'
         self._mode = mode
@@ -448,6 +448,9 @@ def __init__(self, path, mode=None, complevel=None, complib=None,
         self._filters = None
         self.open(mode=mode, **kwargs)
 
+    def __fspath__(self):
+        return self._path
+
     @property
     def root(self):
         """ return the root node """

pandas/tests/io/test_excel.py

@@ -2499,3 +2499,24 @@ def custom_converter(css):
             n_cells += 1
 
     assert n_cells == (10 + 1) * (3 + 1)
+
+
+class TestFSPath(object):
+
+    @pytest.mark.skipif(sys.version_info < (3, 6), reason='requires fspath')
+    def test_excelfile_fspath(self):
+        _skip_if_no_openpyxl
+        with tm.ensure_clean('foo.xlsx') as path:
+            df = DataFrame({"A": [1, 2]})
+            df.to_excel(path)
+            xl = ExcelFile(path)
+            result = os.fspath(xl)
+            assert result == path
+
+    @pytest.mark.skipif(sys.version_info < (3, 6), reason='requires fspath')
+    # @pytest.mark.xfail
+    def test_excelwriter_fspath(self):
+        _skip_if_no_openpyxl
+        with tm.ensure_clean('foo.xlsx') as path:
+            writer = ExcelWriter(path)
+            assert os.fspath(writer) == str(path)

pandas/tests/io/test_pytables.py

@@ -5155,6 +5155,12 @@ def test_query_compare_column_type(self):
                         expected = df.loc[[], :]
                     tm.assert_frame_equal(expected, result)
 
+    @pytest.mark.skipif(sys.version_info < (3, 6), reason="Need python 3.6")
+    def test_fspath(self):
+        with tm.ensure_clean('foo.h5') as path:
+            with pd.HDFStore(path) as store:
+                assert os.fspath(store) == str(path)
+
 
 class TestHDFComplexValues(Base):
     # GH10447