From d73b03324cc51b8ed18408271cebef19a263d162 Mon Sep 17 00:00:00 2001
From: Abraham Flaxman <abie@alum.mit.edu>
Date: Mon, 8 Oct 2012 14:01:27 -0700
Subject: [PATCH] ENH: make None/NaN different from INF/-INF (GH #1919)

---
 pandas/src/tseries.pyx      | 3 ++-
 pandas/src/util.pxd         | 5 ++++-
 pandas/tests/test_common.py | 8 ++++----
 pandas/util/testing.py      | 4 +++-
 4 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/pandas/src/tseries.pyx b/pandas/src/tseries.pyx
index 54641a78a08d9..237b0220aa34d 100644
--- a/pandas/src/tseries.pyx
+++ b/pandas/src/tseries.pyx
@@ -179,7 +179,7 @@ cdef double NEGINF = -INF
 
 cpdef checknull(object val):
     if util.is_float_object(val) or util.is_complex_object(val):
-        return val != val or val == INF or val == NEGINF
+        return val != val and val != INF and val != NEGINF
     elif util.is_datetime64_object(val):
         return get_datetime64_value(val) == NPY_NAT
     elif isinstance(val, _NaT):
@@ -189,6 +189,7 @@ cpdef checknull(object val):
     else:
         return util._checknull(val)
 
+
 def isscalar(object val):
     return np.isscalar(val) or val is None or isinstance(val, _Timestamp)
 
diff --git a/pandas/src/util.pxd b/pandas/src/util.pxd
index fe6e4391c59e5..62bf9dcaa8250 100644
--- a/pandas/src/util.pxd
+++ b/pandas/src/util.pxd
@@ -60,8 +60,11 @@ cdef inline is_array(object o):
 
 
 cdef inline bint _checknull(object val):
+    import numpy as np
+    cdef double INF = <double> np.inf
+    cdef double NEGINF = -INF
     try:
-        return bool(val is None or val != val)
+        return bool(val is None or (val != val and val != INF and val != NEGINF))
     except ValueError:
         return False
 
diff --git a/pandas/tests/test_common.py b/pandas/tests/test_common.py
index e2b0b918f0142..865a9de941c2f 100644
--- a/pandas/tests/test_common.py
+++ b/pandas/tests/test_common.py
@@ -18,8 +18,8 @@ def test_notnull():
     assert notnull(1.)
     assert not notnull(None)
     assert not notnull(np.NaN)
-    assert not notnull(np.inf)
-    assert not notnull(-np.inf)
+    assert notnull(np.inf)
+    assert notnull(-np.inf)
 
     float_series = Series(np.random.randn(5))
     obj_series = Series(np.random.randn(5), dtype=object)
@@ -30,8 +30,8 @@ def test_isnull():
     assert not isnull(1.)
     assert isnull(None)
     assert isnull(np.NaN)
-    assert isnull(np.inf)
-    assert isnull(-np.inf)
+    assert not isnull(np.inf)
+    assert not isnull(-np.inf)
 
     float_series = Series(np.random.randn(5))
     obj_series = Series(np.random.randn(5), dtype=object)
diff --git a/pandas/util/testing.py b/pandas/util/testing.py
index 904426731738a..a15be23c1c4c6 100644
--- a/pandas/util/testing.py
+++ b/pandas/util/testing.py
@@ -103,8 +103,10 @@ def assert_almost_equal(a, b):
         return
 
     if isinstance(a, (bool, float, int)):
+        if np.isinf(a):
+            assert np.isinf(b), err_msg(a,b)
         # case for zero
-        if abs(a) < 1e-5:
+        elif abs(a) < 1e-5:
             np.testing.assert_almost_equal(
                 a, b, decimal=5, err_msg=err_msg(a, b), verbose=False)
         else: