From d623ea0c1de11824cfa49c2e4d5b269ed3b8dabe Mon Sep 17 00:00:00 2001
From: JustinZhengBC <justinzhengbc@gmail.com>
Date: Sat, 8 Dec 2018 19:47:15 -0800
Subject: [PATCH] BUG-16983 fix df.where with extension dtypes

---
 doc/source/whatsnew/v0.24.0.rst     | 1 +
 pandas/core/internals/blocks.py     | 2 ++
 pandas/tests/frame/test_indexing.py | 9 +++++++++
 3 files changed, 12 insertions(+)

diff --git a/doc/source/whatsnew/v0.24.0.rst b/doc/source/whatsnew/v0.24.0.rst
index 0b2b526dfe9e7..0155e70384cfd 100644
--- a/doc/source/whatsnew/v0.24.0.rst
+++ b/doc/source/whatsnew/v0.24.0.rst
@@ -1418,6 +1418,7 @@ Indexing
 - Bug in :func:`Index.union` and :func:`Index.intersection` where name of the ``Index`` of the result was not computed correctly for certain cases (:issue:`9943`, :issue:`9862`)
 - Bug in :class:`Index` slicing with boolean :class:`Index` may raise ``TypeError`` (:issue:`22533`)
 - Bug in ``PeriodArray.__setitem__`` when accepting slice and list-like value (:issue:`23978`)
+- Bug in :func:`DataFrame.where` where a ``ValueError`` would raise when a column had an extension dtype (:issue:`16983`)
 
 Missing
 ^^^^^^^
diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index 51c47a81f8e2f..b68f187d71e41 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -1341,6 +1341,8 @@ def func(cond, values, other):
                 return values
 
             values, other = self._try_coerce_args(values, other)
+            if isinstance(values, ExtensionArray):
+                values = values.get_values().reshape(-1, 1)  # GH 16983
 
             try:
                 return self._try_coerce_result(expressions.where(
diff --git a/pandas/tests/frame/test_indexing.py b/pandas/tests/frame/test_indexing.py
index b95dad422e90a..cc7a4fb28aace 100644
--- a/pandas/tests/frame/test_indexing.py
+++ b/pandas/tests/frame/test_indexing.py
@@ -3089,6 +3089,15 @@ def test_where_tz_values(self, tz_naive_fixture):
         result = df1.where(mask, df2)
         assert_frame_equal(exp, result)
 
+    def test_where_extension_dtypes_with_na(self):
+        from pandas.core.sparse.api import SparseDataFrame
+        sdf = DataFrame(SparseDataFrame([1, None]))
+        cdf = DataFrame([1, None]).astype('category')
+        df = DataFrame([1, None])
+
+        assert_frame_equal(df.where(df.isna()), sdf.where(sdf.isna()))
+        assert_frame_equal(df.where(df.isna()), cdf.where(cdf.isna()))
+
     def test_mask(self):
         df = DataFrame(np.random.randn(5, 3))
         cond = df > 0