change index label default to True and remove None option

Author: charlesdong1991

pandas/core/generic.py

@@ -2871,7 +2871,7 @@ def to_latex(self, buf=None, columns=None, col_space=None, header=True,
             return formatter.buf.getvalue()
 
     def to_csv(self, path_or_buf=None, sep=",", na_rep='', float_format=None,
-               columns=None, header=True, index=True, index_label=None,
+               columns=None, header=True, index=True, index_label=True,
                mode='w', encoding=None, compression='infer', quoting=None,
                quotechar='"', line_terminator=None, chunksize=None,
                tupleize_cols=None, date_format=None, doublequote=True,
@@ -2910,14 +2910,11 @@ def to_csv(self, path_or_buf=None, sep=",", na_rep='', float_format=None,
 
         index : bool, default True
             Write row names (index).
-        index_label : False or str or sequence, default None
-            Column label for index column(s) if desired. If None is given, and
-            `header` and `index` are True, then the index names are used. If
-            `header` is False or None, default index_label changes to False,
-            neither header nor index names will be printed. A
-            sequence should be given if the object uses MultiIndex. If
-            False do not print fields for index names. Use index_label=False
-            for easier importing in R.
+        index_label : bool or str or sequence, default True.
+            Column label for index column(s) if desired. If header or index
+            is False, index_label will be set to False. A sequence should be
+            given if the object uses MultiIndex. If False do not print fields
+            for index names. Use index_label=False for easier importing in R.
         mode : str
             Python write mode, default 'w'.
         encoding : str, optional

pandas/io/formats/csvs.py

@@ -29,7 +29,7 @@ class CSVFormatter(object):
 
     def __init__(self, obj, path_or_buf=None, sep=",", na_rep='',
                  float_format=None, cols=None, header=True, index=True,
-                 index_label=None, mode='w', nanRep=None, encoding=None,
+                 index_label=True, mode='w', nanRep=None, encoding=None,
                  compression='infer', quoting=None, line_terminator='\n',
                  chunksize=None, tupleize_cols=False, quotechar='"',
                  date_format=None, doublequote=True, escapechar=None,
@@ -51,11 +51,14 @@ def __init__(self, obj, path_or_buf=None, sep=",", na_rep='',
         self.header = header
         self.index = index
         self.index_label = index_label
-        # set defualt index label to False if header is False and
-        # index_label is not None or False.
+        # set defualt index label to False if header is False and if
+        # index_label is boolean.
         if self.header is None or self.header is False:
-            if self.index_label is None:
+            if isinstance(self.index_label, bool):
                 self.index_label = False
+        # set index label to False if index is False.
+        if not self.index:
+            self.index_label = False
         self.mode = mode
         if encoding is None:
             encoding = 'ascii' if compat.PY2 else 'utf-8'
@@ -202,7 +205,7 @@ def _index_label_encoder(self):
         """
         index_label = self.index_label
         obj = self.obj
-        if index_label is None:
+        if index_label:
             # append index label based on index type
             if isinstance(obj.index, ABCMultiIndex):
                 index_label = []

pandas/tests/generic/test_frame.py

@@ -274,8 +274,8 @@ def test_deepcopy_empty(self):
     @pytest.mark.skipif(os.name == 'nt',
                         reason="Windows use \r\n for newline")
     @pytest.mark.parametrize("header, index_label, expected", [
-        (False, None, '0,0,0\n1,0,0\n'),
-        (True, None, 'index.name,0,1\n0,0,0\n1,0,0\n'),
+        (False, True, '0,0,0\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')
     ])
@@ -290,8 +290,8 @@ def test_to_csv_header_single_index(self, header, index_label, expected):
     @pytest.mark.skipif(os.name == 'nt',
                         reason="Windows use \r\n for newline")
     @pytest.mark.parametrize("header, index_label, expected", [
-        (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'),
+        (False, True, 'a,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')
     ])