BUG: to_clipboard fails to format output for Excel

doc/source/whatsnew/v0.23.1.txt

@@ -70,7 +70,7 @@ Indexing
 I/O
 ^^^
 
--
+-Bug in :func:`DataFrame.to_clipboard` where data sent to clipboard was not properly tab-delimited even when ``excel=True`` (:issue:`21104`)
 -
 
 Plotting

pandas/io/clipboards.py

@@ -1,6 +1,7 @@
 """ io on the clipboard """
 from pandas import compat, get_option, option_context, DataFrame
 from pandas.compat import StringIO, PY2
+import warnings
 
 
 def read_clipboard(sep=r'\s+', **kwargs):  # pragma: no cover
@@ -55,11 +56,14 @@ def read_clipboard(sep=r'\s+', **kwargs):  # pragma: no cover
 
     counts = {x.lstrip().count('\t') for x in lines}
     if len(lines) > 1 and len(counts) == 1 and counts.pop() != 0:
-        sep = r'\t'
+        sep = '\t'
 
     if sep is None and kwargs.get('delim_whitespace') is None:
         sep = r'\s+'
 
+    if sep == r'\s+' and kwargs.get('engine') is None:
+        kwargs['engine'] = 'python'
+
     return read_table(StringIO(text), sep=sep, **kwargs)
 
 
@@ -99,7 +103,7 @@ def to_clipboard(obj, excel=True, sep=None, **kwargs):  # pragma: no cover
     if excel:
         try:
             if sep is None:
-                sep = r'\t'
+                sep = '\t'
             buf = StringIO()
             # clipboard_set (pyperclip) expects unicode
             obj.to_csv(buf, sep=sep, encoding='utf-8', **kwargs)
@@ -108,8 +112,9 @@ def to_clipboard(obj, excel=True, sep=None, **kwargs):  # pragma: no cover
                 text = text.decode('utf-8')
             clipboard_set(text)
             return
-        except:
-            pass
+        except TypeError:
+            warnings.warn('to_clipboard in excel mode requires a single \
+            character separator. Set "excel=false" or change the separator')
 
     if isinstance(obj, DataFrame):
         # str(df) has various unhelpful defaults, like truncation

pandas/tests/io/test_clipboard.py

@@ -12,7 +12,7 @@
 from pandas.util import testing as tm
 from pandas.util.testing import makeCustomDataframe as mkdf
 from pandas.io.clipboard.exceptions import PyperclipException
-from pandas.io.clipboard import clipboard_set
+from pandas.io.clipboard import clipboard_set, clipboard_get
 
 
 try:
@@ -60,6 +60,9 @@ def setup_class(cls):
         # unicode round trip test for GH 13747, GH 12529
         cls.data['utf8'] = pd.DataFrame({'a': ['µasd', 'Ωœ∑´'],
                                          'b': ['øπ∆˚¬', 'œ∑´®']})
+        # Test for quotes and common delimiters in text
+        cls.data['delim_symbols'] = pd.DataFrame({'a': ['"a,\t"b|c', 'd\tef´'],
+                                                  'b': ['hi\'j', 'k\'\'lm']})
         cls.data_types = list(cls.data.keys())
 
     @classmethod
@@ -69,18 +72,36 @@ def teardown_class(cls):
     def check_round_trip_frame(self, data_type, excel=None, sep=None,
                                encoding=None):
         data = self.data[data_type]
-        data.to_clipboard(excel=excel, sep=sep, encoding=encoding)
-        if sep is not None:
-            result = read_clipboard(sep=sep, index_col=0, encoding=encoding)
+        if excel in [None, True] and sep is not None and len(sep) > 1:
+            with tm.assert_produces_warning():
+                data.to_clipboard(excel=excel, sep=sep, encoding=encoding)
         else:
-            result = read_clipboard(encoding=encoding)
-        tm.assert_frame_equal(data, result, check_dtype=False)
+            data.to_clipboard(excel=excel, sep=sep, encoding=encoding)
+
+            if excel in [None, True] and sep is not None:
+                # Expect Excel
+                result = read_clipboard(sep=sep, index_col=0,
+                                        encoding=encoding)
+            elif excel in [None, True] and sep is None:
+                # Expect Excel with tabs
+                result = read_clipboard(sep='\t', index_col=0,
+                                        encoding=encoding)
+            else:
+                # Expect df.__repr__ format
+                result = read_clipboard(encoding=encoding)
+
+            if excel in [None, True]:
+                tm.assert_frame_equal(data, result, check_dtype=False)
+            else:
+                assert data.to_string() == result.to_string()
+                assert data.shape == result.shape
 
     def test_round_trip_frame_sep(self):
         for dt in self.data_types:
             self.check_round_trip_frame(dt, sep=',')
             self.check_round_trip_frame(dt, sep=r'\s+')
             self.check_round_trip_frame(dt, sep='|')
+            self.check_round_trip_frame(dt, sep='\t')
 
     def test_round_trip_frame_string(self):
         for dt in self.data_types:
@@ -124,6 +145,34 @@ def test_read_clipboard_infer_excel(self):
 
         tm.assert_frame_equal(res, exp)
 
+    def test_excel_clipboard_tabs(self):
+        for dt in self.data_types:
+            for sep in ['\t', None, 'default', ',', '|']:
+                for excel in [True, None, 'default', False]:
+                    # Function default should be to to produce tab delimited
+                    kwargs = {}
+                    if excel != 'default':
+                        kwargs['excel'] = excel
+                    if sep != 'default':
+                        kwargs['sep'] = sep
+                    data = self.data[dt]
+                    data.to_clipboard(**kwargs)
+                    if sep in ['\t', None, 'default'] and excel is not False:
+                        # Expect tab delimited
+                        result = read_clipboard(sep='\t', index_col=0)
+                        tm.assert_frame_equal(data, result, check_dtype=False)
+                        assert clipboard_get().count('\t') > 0
+                    elif excel is False:
+                        # Expect spaces (ie. df.__repr__() default)
+                        result = read_clipboard(sep=r'\s+')
+                        assert result.to_string() == data.to_string()
+                        assert data.shape == result.shape
+                    else:
+                        # Expect other delimited ',' and '|'
+                        result = read_clipboard(sep=sep, index_col=0)
+                        tm.assert_frame_equal(data, result, check_dtype=False)
+                        assert clipboard_get().count(sep) > 0
+
     def test_invalid_encoding(self):
         # test case for testing invalid encoding
         data = self.data['string']