CLN: Improve Exceptions in core/common, io/excel and core/format

doc/source/release.rst

@@ -71,6 +71,8 @@ pandas 0.13
     when the key is a column
   - Support for using a ``DatetimeIndex/PeriodsIndex`` directly in a datelike calculation
     e.g. s-s.index (:issue:`4629`)
+  - Better/cleaned up exceptions in core/common, io/excel and core/format.
+    (:issue:`4721`, :issue:`3954`)
 
 **API Changes**
 

pandas/core/common.py

@@ -541,7 +541,7 @@ def take_nd(arr, indexer, axis=0, out=None, fill_value=np.nan,
                     mask_info = mask, needs_masking
                 if needs_masking:
                     if out is not None and out.dtype != dtype:
-                        raise Exception('Incompatible type for fill_value')
+                        raise TypeError('Incompatible type for fill_value')
                 else:
                     # if not, then depromote, set fill_value to dummy
                     # (it won't be used but we don't want the cython code
@@ -612,7 +612,7 @@ def take_2d_multi(arr, indexer, out=None, fill_value=np.nan,
                     mask_info = (row_mask, col_mask), (row_needs, col_needs)
                 if row_needs or col_needs:
                     if out is not None and out.dtype != dtype:
-                        raise Exception('Incompatible type for fill_value')
+                        raise TypeError('Incompatible type for fill_value')
                 else:
                     # if not, then depromote, set fill_value to dummy
                     # (it won't be used but we don't want the cython code
@@ -857,8 +857,8 @@ def changeit():
 
                 # if we are trying to do something unsafe
                 # like put a bigger dtype in a smaller one, use the smaller one
-                if change.dtype.itemsize < r.dtype.itemsize:
-                    raise Exception(
+                if change.dtype.itemsize < r.dtype.itemsize: # pragma: no cover
+                    raise AssertionError(
                         "cannot change dtype of input to smaller size")
                 change.dtype = r.dtype
                 change[:] = r
@@ -1159,8 +1159,8 @@ def interpolate_2d(values, method='pad', axis=0, limit=None, fill_value=None):
     # reshape a 1 dim if needed
     ndim = values.ndim
     if values.ndim == 1:
-        if axis != 0:
-            raise Exception("cannot interpolate on a ndim == 1 with axis != 0")
+        if axis != 0: # pragma: no cover
+            raise AssertionError("cannot interpolate on a ndim == 1 with axis != 0")
         values = values.reshape(tuple((1,) + values.shape))
 
     if fill_value is None:
@@ -1434,13 +1434,17 @@ def ensure_float(arr):
     return arr
 
 
-def _mut_exclusive(arg1, arg2):
-    if arg1 is not None and arg2 is not None:
-        raise Exception('mutually exclusive arguments')
-    elif arg1 is not None:
-        return arg1
+def _mut_exclusive(**kwargs):
+    item1, item2 = kwargs.items()
+    label1, val1 = item1
+    label2, val2 = item2
+    if val1 is not None and val2 is not None:
+        raise TypeError('mutually exclusive arguments: %r and %r' %
+                        (label1, label2))
+    elif val1 is not None:
+        return val1
     else:
-        return arg2
+        return val2
 
 
 def _any_none(*args):

pandas/core/format.py

@@ -1,13 +1,13 @@
 from __future__ import print_function
 # pylint: disable=W0141
 
-from pandas import compat
 import sys
 
-from pandas.compat import StringIO, lzip, range, map, zip, reduce, u, OrderedDict
 from pandas.core.common import adjoin, isnull, notnull
 from pandas.core.index import Index, MultiIndex, _ensure_index
 from pandas import compat
+from pandas.compat import(StringIO, lzip, range, map, zip, reduce, u,
+                          OrderedDict)
 from pandas.util.terminal import get_terminal_size
 from pandas.core.config import get_option, set_option, reset_option
 import pandas.core.common as com
@@ -356,7 +356,7 @@ def get_col_type(dtype):
                 column_format = 'l%s' % ''.join(map(get_col_type, dtypes))
             else:
                 column_format = '%s' % ''.join(map(get_col_type, dtypes))
-        elif not isinstance(column_format, compat.string_types):
+        elif not isinstance(column_format, compat.string_types):  # pragma: no cover
             raise AssertionError(('column_format must be str or unicode, not %s'
                                   % type(column_format)))
 
@@ -820,8 +820,9 @@ def __init__(self, obj, path_or_buf, sep=",", na_rep='', float_format=None,
 
         # validate mi options
         if self.has_mi_columns:
-            if cols is not None:
-                raise Exception("cannot specify cols with a multi_index on the columns")
+            # guarded against in to_csv itself
+            if cols is not None: # pragma: no cover
+                raise AssertionError("cannot specify cols with a multi_index on the columns")
 
         if cols is not None:
             if isinstance(cols,Index):

pandas/io/excel.py

@@ -73,7 +73,7 @@ def __init__(self, path_or_buf, **kwds):
         import xlrd  # throw an ImportError if we need to
 
         ver = tuple(map(int, xlrd.__VERSION__.split(".")[:2]))
-        if ver < (0, 9):
+        if ver < (0, 9):  # pragma: no cover
             raise ImportError("pandas requires xlrd >= 0.9.0 for excel "
                               "support, current version " + xlrd.__VERSION__)
 
@@ -382,8 +382,8 @@ def write_cells(self, cells, sheet_name=None, startrow=0, startcol=0):
         if sheet_name is None:
             sheet_name = self.cur_sheet
         if sheet_name is None:  # pragma: no cover
-            raise Exception('Must pass explicit sheet_name or set '
-                            'cur_sheet property')
+            raise ValueError('Must pass explicit sheet_name or set '
+                             'cur_sheet property')
         if self.use_xlsx:
             self._writecells_xlsx(cells, sheet_name, startrow, startcol)
         else:

pandas/sparse/panel.py

@@ -319,8 +319,8 @@ def reindex(self, major=None, items=None, minor=None, major_axis=None,
         -------
         reindexed : SparsePanel
         """
-        major = com._mut_exclusive(major, major_axis)
-        minor = com._mut_exclusive(minor, minor_axis)
+        major = com._mut_exclusive(major=major, major_axis=major_axis)
+        minor = com._mut_exclusive(minor=minor, minor_axis=minor_axis)
 
         if com._all_none(items, major, minor):
             raise ValueError('Must specify at least one axis')

pandas/tests/test_common.py

@@ -20,6 +20,14 @@
 _multiprocess_can_split_ = True
 
 
+def test_mut_exclusive():
+    msg = "mutually exclusive arguments: '[ab]' and '[ab]'"
+    with tm.assertRaisesRegexp(TypeError, msg):
+        com._mut_exclusive(a=1, b=2)
+    assert com._mut_exclusive(a=1, b=None) == 1
+    assert com._mut_exclusive(major=None, major_axis=None) is None
+
+
 def test_is_sequence():
     is_seq = com._is_sequence
     assert(is_seq((1, 2)))
@@ -360,6 +368,8 @@ def test_is_recompilable():
 
 
 class TestTake(unittest.TestCase):
+    # standard incompatible fill error
+    fill_error = re.compile("Incompatible type for fill_value")
 
     _multiprocess_can_split_ = True
 
@@ -381,8 +391,8 @@ def _test_dtype(dtype, can_hold_na):
                 expected[3] = np.nan
                 tm.assert_almost_equal(out, expected)
             else:
-                self.assertRaises(Exception, com.take_1d, data,
-                                  indexer, out=out)
+                with tm.assertRaisesRegexp(TypeError, self.fill_error):
+                    com.take_1d(data, indexer, out=out)
                 # no exception o/w
                 data.take(indexer, out=out)
 
@@ -466,13 +476,11 @@ def _test_dtype(dtype, can_hold_na):
                 tm.assert_almost_equal(out0, expected0)
                 tm.assert_almost_equal(out1, expected1)
             else:
-                self.assertRaises(Exception, com.take_nd, data,
-                                  indexer, out=out0, axis=0)
-                self.assertRaises(Exception, com.take_nd, data,
-                                  indexer, out=out1, axis=1)
-                # no exception o/w
-                data.take(indexer, out=out0, axis=0)
-                data.take(indexer, out=out1, axis=1)
+                for i, out in enumerate([out0, out1]):
+                    with tm.assertRaisesRegexp(TypeError, self.fill_error):
+                        com.take_nd(data, indexer, out=out, axis=i)
+                    # no exception o/w
+                    data.take(indexer, out=out, axis=i)
 
         _test_dtype(np.float64, True)
         _test_dtype(np.float32, True)
@@ -572,16 +580,11 @@ def _test_dtype(dtype, can_hold_na):
                 tm.assert_almost_equal(out1, expected1)
                 tm.assert_almost_equal(out2, expected2)
             else:
-                self.assertRaises(Exception, com.take_nd, data,
-                                  indexer, out=out0, axis=0)
-                self.assertRaises(Exception, com.take_nd, data,
-                                  indexer, out=out1, axis=1)
-                self.assertRaises(Exception, com.take_nd, data,
-                                  indexer, out=out2, axis=2)
-                # no exception o/w
-                data.take(indexer, out=out0, axis=0)
-                data.take(indexer, out=out1, axis=1)
-                data.take(indexer, out=out2, axis=2)
+                for i, out in enumerate([out0, out1, out2]):
+                    with tm.assertRaisesRegexp(TypeError, self.fill_error):
+                        com.take_nd(data, indexer, out=out, axis=i)
+                    # no exception o/w
+                    data.take(indexer, out=out, axis=i)
 
         _test_dtype(np.float64, True)
         _test_dtype(np.float32, True)