From bd57c50d79a26e78fb7f94c91c8e6db40bb79617 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 27 Jan 2020 17:10:53 -0800
Subject: [PATCH 1/3] require values_from_object before expressions calls

---
 pandas/core/computation/expressions.py | 19 +++++--------------
 pandas/core/internals/blocks.py        |  8 +++++---
 2 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/pandas/core/computation/expressions.py b/pandas/core/computation/expressions.py
index ada983e9e4fad..51750b14dc585 100644
--- a/pandas/core/computation/expressions.py
+++ b/pandas/core/computation/expressions.py
@@ -12,8 +12,6 @@
 
 from pandas._config import get_option
 
-from pandas._libs.lib import values_from_object
-
 from pandas.core.dtypes.generic import ABCDataFrame
 
 from pandas.core.computation.check import _NUMEXPR_INSTALLED
@@ -123,26 +121,19 @@ def _evaluate_numexpr(op, op_str, a, b):
 
 
 def _where_standard(cond, a, b):
-    return np.where(
-        values_from_object(cond), values_from_object(a), values_from_object(b)
-    )
+    # Caller is responsible for calling values_from_object if necessary
+    return np.where(cond, a, b)
 
 
 def _where_numexpr(cond, a, b):
+    # Caller is responsible for calling values_from_object if necessary
     result = None
 
     if _can_use_numexpr(None, "where", a, b, "where"):
-        cond_value = getattr(cond, "values", cond)
-        a_value = getattr(a, "values", a)
-        b_value = getattr(b, "values", b)
 
         result = ne.evaluate(
             "where(cond_value, a_value, b_value)",
-            local_dict={
-                "cond_value": cond_value,
-                "a_value": a_value,
-                "b_value": b_value,
-            },
+            local_dict={"cond_value": cond, "a_value": a, "b_value": b,},
             casting="safe",
         )
 
@@ -187,7 +178,7 @@ def _bool_arith_check(
     return True
 
 
-def evaluate(op, op_str, a, b, use_numexpr=True):
+def evaluate(op, op_str, a, b, use_numexpr: bool = True):
     """
     Evaluate and return the expression of the op on a and b.
 
diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index a93211edf162b..80369081f96d6 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -1379,8 +1379,7 @@ def where(
         if not hasattr(cond, "shape"):
             raise ValueError("where must have a condition that is ndarray like")
 
-        # our where function
-        def func(cond, values, other):
+        def where_func(cond, values, other):
 
             if not (
                 (self.is_integer or self.is_bool)
@@ -1391,8 +1390,11 @@ def func(cond, values, other):
                 if not self._can_hold_element(other):
                     raise TypeError
                 if lib.is_scalar(other) and isinstance(values, np.ndarray):
+                    # convert datetime to datetime64, timedelta to timedelta64
                     other = convert_scalar(values, other)
 
+            # By the time we get here, we should have all Series/Index
+            #  args extracted to  ndarray
             fastres = expressions.where(cond, values, other)
             return fastres
 
@@ -1402,7 +1404,7 @@ def func(cond, values, other):
             # see if we can operate on the entire block, or need item-by-item
             # or if we are a single block (ndim == 1)
             try:
-                result = func(cond, values, other)
+                result = where_func(cond, values, other)
             except TypeError:
 
                 # we cannot coerce, return a compat dtype

From 058194589b1c858f367c94788cbe4f21667b9595 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 27 Jan 2020 17:11:52 -0800
Subject: [PATCH 2/3] lint

---
 pandas/core/computation/expressions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/computation/expressions.py b/pandas/core/computation/expressions.py
index 51750b14dc585..4ee2c993d112d 100644
--- a/pandas/core/computation/expressions.py
+++ b/pandas/core/computation/expressions.py
@@ -133,7 +133,7 @@ def _where_numexpr(cond, a, b):
 
         result = ne.evaluate(
             "where(cond_value, a_value, b_value)",
-            local_dict={"cond_value": cond, "a_value": a, "b_value": b,},
+            local_dict={"cond_value": cond, "a_value": a, "b_value": b},
             casting="safe",
         )
 

From 0060284dc57b341400fddda39bbee9c5a5b08b5e Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 27 Jan 2020 17:51:32 -0800
Subject: [PATCH 3/3] mypy fixup

---
 pandas/core/computation/expressions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/computation/expressions.py b/pandas/core/computation/expressions.py
index 4ee2c993d112d..fdc299ccdfde8 100644
--- a/pandas/core/computation/expressions.py
+++ b/pandas/core/computation/expressions.py
@@ -178,7 +178,7 @@ def _bool_arith_check(
     return True
 
 
-def evaluate(op, op_str, a, b, use_numexpr: bool = True):
+def evaluate(op, op_str, a, b, use_numexpr=True):
     """
     Evaluate and return the expression of the op on a and b.