Added comments and edited the whatsnew.

Author: Nicholas Ver Halen

doc/source/whatsnew/v0.19.2.txt

@@ -25,4 +25,4 @@ Bug Fixes
 
 - compat with ``dateutil==2.6.0`` for testing (:issue:`14621`)
 - allow ``nanoseconds`` in ``Timestamp.replace`` kwargs (:issue:`14621`)
-- Bug in ``pd.to_numeric`` where a 0 was not unsigned on a downcast = 'unsigned' argument (:issue:`14401`)
+- Bug in ``pd.to_numeric`` where a 0 was not unsigned on a ``downcast = "unsigned"`` argument (:issue:`14401`)

pandas/tools/tests/test_util.py

@@ -4,8 +4,7 @@
 import nose
 
 import numpy as np
-from numpy import (iinfo, int8, int16, int32, int64,
-                   uint8, uint16, uint32,)
+from numpy import iinfo
 
 import pandas as pd
 from pandas import (date_range, Index, _np_version_under1p9)
@@ -412,23 +411,25 @@ def test_downcast_limits(self):
         i = 'integer'
         u = 'unsigned'
         dtype_downcast_min_max = [
-            ('int8', i, [iinfo(int8).min, iinfo(int8).max]),
-            ('int16', i, [iinfo(int16).min, iinfo(int16).max]),
-            ('int32', i, [iinfo(int32).min, iinfo(int32).max]),
-            ('int64', i, [iinfo(int64).min, iinfo(int64).max]),
-            ('uint8', u, [iinfo(uint8).min, iinfo(uint8).max]),
-            ('uint16', u, [iinfo(uint16).min, iinfo(uint16).max]),
-            ('uint32', u, [iinfo(uint32).min, iinfo(uint32).max]),
+            ('int8', i, [iinfo(np.int8).min, iinfo(np.int8).max]),
+            ('int16', i, [iinfo(np.int16).min, iinfo(np.int16).max]),
+            ('int32', i, [iinfo(np.int32).min, iinfo(np.int32).max]),
+            ('int64', i, [iinfo(np.int64).min, iinfo(np.int64).max]),
+            ('uint8', u, [iinfo(np.uint8).min, iinfo(np.uint8).max]),
+            ('uint16', u, [iinfo(np.uint16).min, iinfo(np.uint16).max]),
+            ('uint32', u, [iinfo(np.uint32).min, iinfo(np.uint32).max]),
+            # Test will be skipped until there is more uint64 support.
             # ('uint64', u, [iinfo(uint64).min, iinfo(uint64).max]),
-            ('int16', i, [iinfo(int8).min, iinfo(int8).max + 1]),
-            ('int32', i, [iinfo(int16).min, iinfo(int16).max + 1]),
-            ('int64', i, [iinfo(int32).min, iinfo(int32).max + 1]),
-            ('int16', i, [iinfo(int8).min - 1, iinfo(int16).max]),
-            ('int32', i, [iinfo(int16).min - 1, iinfo(int32).max]),
-            ('int64', i, [iinfo(int32).min - 1, iinfo(int64).max]),
-            ('uint16', u, [iinfo(uint8).min, iinfo(uint8).max + 1]),
-            ('uint32', u, [iinfo(uint16).min, iinfo(uint16).max + 1]),
-            # ('uint64', u, [iinfo(uint32).min, iinfo(uint32).max + 1]),
+            ('int16', i, [iinfo(np.int8).min, iinfo(np.int8).max + 1]),
+            ('int32', i, [iinfo(np.int16).min, iinfo(np.int16).max + 1]),
+            ('int64', i, [iinfo(np.int32).min, iinfo(np.int32).max + 1]),
+            ('int16', i, [iinfo(np.int8).min - 1, iinfo(np.int16).max]),
+            ('int32', i, [iinfo(np.int16).min - 1, iinfo(np.int32).max]),
+            ('int64', i, [iinfo(np.int32).min - 1, iinfo(np.int64).max]),
+            ('uint16', u, [iinfo(np.uint8).min, iinfo(np.uint8).max + 1]),
+            ('uint32', u, [iinfo(np.uint16).min, iinfo(np.uint16).max + 1]),
+            # Test will be skipped until there is more uint64 support.
+            # ('uint64', u, [iinfo(np.uint32).min, iinfo(np.uint32).max + 1]),
         ]
 
         for dtype, downcast, min_max in dtype_downcast_min_max: