changes based on simon review and fix linting error that breaks the pr

Author: charlesdong1991

pandas/core/generic.py

@@ -2910,7 +2910,7 @@ def to_csv(self, path_or_buf=None, sep=",", na_rep='', float_format=None,
 
         index : bool, default True
             Write row names (index).
-        index_label : bool or str or sequence, default None.
+        index_label : bool or str or sequence, default None
             If index_label is not explicitly called, False if either header
             or index is set to False; otherwise, True. If index_label is
             explicitly called by allowed types of input, then input will be

pandas/tests/generic/test_frame.py

@@ -270,40 +270,3 @@ def test_deepcopy_empty(self):
         empty_frame_copy = deepcopy(empty_frame)
 
         self._compare(empty_frame_copy, empty_frame)
-
-    @pytest.mark.skipif(os.name == 'nt',
-                        reason="Windows use \r\n for newline")
-    @pytest.mark.parametrize("header, index_label, expected", [
-        (False, True, 'index.name,,\n0,0,0\n1,0,0\n'),
-        (True, True, 'index.name,0,1\n0,0,0\n1,0,0\n'),
-        (False, False, '0,0,0\n1,0,0\n'),
-        (True, False, ',0,1\n0,0,0\n1,0,0\n'),
-        (False, None, '0,0,0\n1,0,0\n'),
-        (True, None, 'index.name,0,1\n0,0,0\n1,0,0\n')
-    ])
-    def test_to_csv_header_single_index(self, header, index_label, expected):
-        # issue 24546
-        df = pd.DataFrame(np.zeros((2, 2), dtype=int))
-        df.index.name = 'index.name'
-
-        result = df.to_csv(header=header, index_label=index_label)
-        assert result == expected
-
-    @pytest.mark.skipif(os.name == 'nt',
-                        reason="Windows use \r\n for newline")
-    @pytest.mark.parametrize("header, index_label, expected", [
-        (False, True, 'index.name.0,index.name.1,,\na,b,0,0\na,c,0,0\n'),
-        (True, True, 'index.name.0,index.name.1,0,1\na,b,0,0\na,c,0,0\n'),
-        (False, False, 'a,b,0,0\na,c,0,0\n'),
-        (True, False, ',,0,1\na,b,0,0\na,c,0,0\n'),
-        (False, None, 'a,b,0,0\na,c,0,0\n'),
-        (True, None, 'index.name.0,index.name.1,0,1\na,b,0,0\na,c,0,0\n')
-    ])
-    def test_to_csv_header_multi_index(self, header, index_label, expected):
-        # issue 24546
-        df = pd.DataFrame(np.zeros((2, 2), dtype=int))
-        df.index = pd.MultiIndex.from_product([['a'], ['b', 'c']], names=[
-            'index.name.0', 'index.name.1'])
-
-        result = df.to_csv(header=header, index_label=index_label)
-        assert result == expected

pandas/tests/io/formats/test_to_csv.py

@@ -561,3 +561,42 @@ def test_to_csv_compression(self, compression_only,
             result = pd.read_csv(path, index_col=0,
                                  compression=read_compression)
             tm.assert_frame_equal(result, df)
+
+    @pytest.mark.parametrize("header, index_label, expected_rows", [
+        (False, True, ['index.name,,', '0,0,0', '1,0,0']),
+        (True, True, ['index.name,A,B', '0,0,0', '1,0,0']),
+        (False, False, ['0,0,0', '1,0,0']),
+        (True, False, [',A,B', '0,0,0', '1,0,0']),
+        (False, None, ['0,0,0', '1,0,0']),
+        (True, None, ['index.name,A,B', '0,0,0', '1,0,0'])
+    ])
+    def test_to_csv_header_single_index(self, header, index_label,
+                                        expected_rows):
+        # issue 24546
+        df = pd.DataFrame(np.zeros((2, 2), dtype=int))
+        df.index.name = 'index.name'
+        df.columns = ['A', 'B']
+
+        result = df.to_csv(header=header, index_label=index_label)
+        expected = tm.convert_rows_list_to_csv_str(expected_rows)
+        assert result == expected
+
+    @pytest.mark.parametrize("header, index_label, expected_rows", [
+        (False, True, ['index.name.0,index.name.1,,', 'a,b,0,0', 'a,c,0,0']),
+        (True, True, ['index.name.0,index.name.1,A,B', 'a,b,0,0', 'a,c,0,0']),
+        (False, False, ['a,b,0,0', 'a,c,0,0']),
+        (True, False, [',,A,B', 'a,b,0,0', 'a,c,0,0']),
+        (False, None, ['a,b,0,0', 'a,c,0,0']),
+        (True, None, ['index.name.0,index.name.1,A,B', 'a,b,0,0', 'a,c,0,0'])
+    ])
+    def test_to_csv_header_multi_index(self, header, index_label,
+                                       expected_rows):
+        # issue 24546
+        df = pd.DataFrame(np.zeros((2, 2), dtype=int))
+        df.columns = ['A', 'B']
+        df.index = pd.MultiIndex.from_product([['a'], ['b', 'c']], names=[
+            'index.name.0', 'index.name.1'])
+
+        result = df.to_csv(header=header, index_label=index_label)
+        expected = tm.convert_rows_list_to_csv_str(expected_rows)
+        assert result == expected