BUG: to_clipboard fails to format output for Excel

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 +56,27 @@ 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'
 
+    # Edge case where sep is specified to be None
     if sep is None and kwargs.get('delim_whitespace') is None:
         sep = r'\s+'
 
+    # Regex separator currently only works with python engine.
+    # Default to python if separator is multi-character (regex)
+    if len(sep) > 1 and kwargs.get('engine') is None:
+        kwargs['engine'] = 'python'
+    elif len(sep) > 1 and kwargs.get('engine') == 'c':
+        warnings.warn('from_clipboard with regex separator does not work'
+                      ' properly with c engine')
+
+    # In PY2, the c table reader first encodes text with UTF-8 but Python
+    # table reader uses the format of the passed string.
+    # For PY2, encode strings first so that output from python and c
+    # engines produce consistent results
+    if kwargs.get('engine') == 'python' and compat.PY2:
+        text = text.encode('utf-8')
+
     return read_table(StringIO(text), sep=sep, **kwargs)
 
 
@@ -99,7 +116,7 @@ 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 +125,10 @@ 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

@@ -66,6 +66,15 @@ def setup_class(cls):
     def teardown_class(cls):
         del cls.data_types, cls.data
 
+    def test_read_delim_warning(self):
+        with tm.assert_produces_warning():
+            self.data['string'].to_clipboard()
+            pd.read_clipboard(sep=r'\s+', engine='c')
+
+    def test_write_delim_warning(self):
+        with tm.assert_produces_warning():
+            self.data['string'].to_clipboard(excel=True, sep=r'\s+')
+
     def check_round_trip_frame(self, data_type, excel=None, sep=None,
                                encoding=None):
         data = self.data[data_type]