BUG: Validate the ordered parameter for Categorical (pandas-dev#14059)

Closes pandas-devgh-14058.

Author: gfyoung

doc/source/whatsnew/v0.19.0.txt

@@ -967,6 +967,7 @@ Bug Fixes
 - Bug in ``DataFrame`` assignment with an object-dtyped ``Index`` where the resultant column is mutable to the original object. (:issue:`13522`)
 - Bug in matplotlib ``AutoDataFormatter``; this restores the second scaled formatting and re-adds micro-second scaled formatting (:issue:`13131`)
 - Bug in selection from a ``HDFStore`` with a fixed format and ``start`` and/or ``stop`` specified will now return the selected range (:issue:`8287`)
+- Bug in ``Categorical.from_codes()`` where an unhelpful error was raised when an invalid ``ordered`` parameter was passed in (:issue:`14058`)
 - Bug in ``Series`` construction from a tuple of integers on windows not returning default dtype (int64) (:issue:`13646`)
 
 - Bug in ``.groupby(..).resample(..)`` when the same object is called multiple times (:issue:`13174`)

pandas/core/categorical.py

@@ -231,6 +231,8 @@ class Categorical(PandasObject):
     def __init__(self, values, categories=None, ordered=False,
                  name=None, fastpath=False):
 
+        self._validate_ordered(ordered)
+
         if fastpath:
             # fast path
             self._codes = _coerce_indexer_dtype(values, categories)
@@ -502,6 +504,25 @@ def _get_labels(self):
 
     _categories = None
 
+    @classmethod
+    def _validate_ordered(cls, ordered):
+        """
+        Validates that we have a valid ordered parameter. If
+        it is not a boolean, a TypeError will be raised.
+
+        Parameters
+        ----------
+        ordered : object
+            The parameter to be verified.
+
+        Raises
+        ------
+        TypeError
+            If 'ordered' is not a boolean.
+        """
+        if not is_bool(ordered):
+            raise TypeError("'ordered' must either be 'True' or 'False'")
+
     @classmethod
     def _validate_categories(cls, categories, fastpath=False):
         """
@@ -588,8 +609,7 @@ def set_ordered(self, value, inplace=False):
            Whether or not to set the ordered attribute inplace or return a copy
            of this categorical with ordered set to the value
         """
-        if not is_bool(value):
-            raise TypeError("ordered must be a boolean value")
+        self._validate_ordered(value)
         cat = self if inplace else self.copy()
         cat._ordered = value
         if not inplace:

pandas/indexes/category.py

@@ -123,6 +123,7 @@ def _create_categorical(self, data, categories=None, ordered=None):
         Categorical
         """
         if not isinstance(data, ABCCategorical):
+            ordered = False if ordered is None else ordered
             from pandas.core.categorical import Categorical
             data = Categorical(data, categories=categories, ordered=ordered)
         else:

pandas/tests/test_categorical.py

@@ -398,6 +398,24 @@ def f():
             codes = np.random.choice([0, 1], 5, p=[0.9, 0.1])
             pd.Categorical.from_codes(codes, categories=["train", "test"])
 
+    def test_validate_ordered(self):
+        # see gh-14058
+        exp_msg = "'ordered' must either be 'True' or 'False'"
+        exp_err = TypeError
+
+        # This should be a boolean.
+        ordered = np.array([0, 1, 2])
+
+        with tm.assertRaisesRegexp(exp_err, exp_msg):
+            Categorical([1, 2, 3], ordered=ordered)
+
+        with tm.assertRaisesRegexp(exp_err, exp_msg):
+            Categorical.from_array([1, 2, 3], ordered=ordered)
+
+        with tm.assertRaisesRegexp(exp_err, exp_msg):
+            Categorical.from_codes([0, 0, 1], categories=['a', 'b', 'c'],
+                                   ordered=ordered)
+
     def test_comparisons(self):
 
         result = self.factor[self.factor == 'a']