From 43a5c24bce3bdeeeead41367e3746e8684a3f292 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Sun, 15 Mar 2020 12:51:46 -0700
Subject: [PATCH 1/3] BUG: arithmetic with reindex pow

---
 pandas/core/ops/__init__.py           | 10 ++++++++--
 pandas/tests/frame/test_arithmetic.py | 10 ++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/pandas/core/ops/__init__.py b/pandas/core/ops/__init__.py
index ed779c5da6d14..3153a9ac28c10 100644
--- a/pandas/core/ops/__init__.py
+++ b/pandas/core/ops/__init__.py
@@ -711,13 +711,17 @@ def to_series(right):
 
 
 def _should_reindex_frame_op(
-    left: "DataFrame", right, axis, default_axis: int, fill_value, level
+    left: "DataFrame", right, op, axis, default_axis: int, fill_value, level
 ) -> bool:
     """
     Check if this is an operation between DataFrames that will need to reindex.
     """
     assert isinstance(left, ABCDataFrame)
 
+    if op is operator.pow or op is rpow:
+        # GH#32685 pow has special semantics for operating with null values
+        return False
+
     if not isinstance(right, ABCDataFrame):
         return False
 
@@ -779,7 +783,9 @@ def _arith_method_FRAME(cls, op, special):
     @Appender(doc)
     def f(self, other, axis=default_axis, level=None, fill_value=None):
 
-        if _should_reindex_frame_op(self, other, axis, default_axis, fill_value, level):
+        if _should_reindex_frame_op(
+            self, other, op, axis, default_axis, fill_value, level
+        ):
             return _frame_arith_method_with_reindex(self, other, op)
 
         self, other = _align_method_FRAME(self, other, axis, flex=True, level=level)
diff --git a/pandas/tests/frame/test_arithmetic.py b/pandas/tests/frame/test_arithmetic.py
index 92d86c8b602ff..5b2127a51c6c2 100644
--- a/pandas/tests/frame/test_arithmetic.py
+++ b/pandas/tests/frame/test_arithmetic.py
@@ -823,3 +823,13 @@ def test_align_frame(self):
         half = ts[::2]
         result = ts + half.take(np.random.permutation(len(half)))
         tm.assert_frame_equal(result, expected)
+
+
+def test_pow_with_realignment():
+    # GH#32685 pow has special semantics for operating with null values
+    left = pd.DataFrame({"A": [0, 1, 2]})
+    right = pd.DataFrame(index=[0, 1, 2])
+
+    result = left ** right
+    expected = pd.DataFrame({"A": [np.nan, 1.0, np.nan]})
+    tm.assert_frame_equal(result, expected)

From 7a8217395b9141834209876f3266c72f318005f9 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 16 Mar 2020 10:11:21 -0700
Subject: [PATCH 2/3] update tests

---
 pandas/tests/frame/test_arithmetic.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/pandas/tests/frame/test_arithmetic.py b/pandas/tests/frame/test_arithmetic.py
index 5b2127a51c6c2..b39c58b9931ab 100644
--- a/pandas/tests/frame/test_arithmetic.py
+++ b/pandas/tests/frame/test_arithmetic.py
@@ -833,3 +833,17 @@ def test_pow_with_realignment():
     result = left ** right
     expected = pd.DataFrame({"A": [np.nan, 1.0, np.nan]})
     tm.assert_frame_equal(result, expected)
+
+
+# TODO: move to tests.arithmetic and parametrize
+def test_pow_nan_with_zero():
+    left = pd.DataFrame({"A": [np.nan, np.nan, np.nan]})
+    right = pd.DataFrame({"A": [0, 0, 0]})
+
+    expected = pd.DataFrame({"A": [1.0, 1.0, 1.0]})
+
+    result = left ** right
+    tm.assert_frame_equal(result, expected)
+
+    result = left["A"] ** right["A"]
+    tm.assert_series_equal(result, expected["A"])

From 7b606f1ede65a81458b2a13d982d015275242a5d Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 16 Mar 2020 10:12:17 -0700
Subject: [PATCH 3/3] whatsnew

---
 doc/source/whatsnew/v1.0.3.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v1.0.3.rst b/doc/source/whatsnew/v1.0.3.rst
index 17f1bdc365518..00d548c2cee63 100644
--- a/doc/source/whatsnew/v1.0.3.rst
+++ b/doc/source/whatsnew/v1.0.3.rst
@@ -15,6 +15,7 @@ including other versions of pandas.
 
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
+- Fixed regression in :class:`DataFrame` exponentiation with reindexing (:issue:`32685`)
 
 .. _whatsnew_103.bug_fixes: