ENH: Allow for an in-place nan_to_num conversion. Fixes #8634

2 files changed, 19 insertions, 2 deletions

diff --git a/numpy/lib/tests/test_type_check.py b/numpy/lib/tests/test_type_check.py
index 4523e3f24..473b558be 100644
--- a/numpy/lib/tests/test_type_check.py
+++ b/numpy/lib/tests/test_type_check.py
@@ -320,6 +320,16 @@ class TestNanToNum(TestCase):
         assert_(vals[1] == 0)
         assert_all(vals[2] > 1e10) and assert_all(np.isfinite(vals[2]))
 
+        # perform the same test but in-place
+        with np.errstate(divide='ignore', invalid='ignore'):
+            vals = np.array((-1., 0, 1))/0.
+        result = nan_to_num(vals, copy=False)
+
+        assert_(result is vals)
+        assert_all(vals[0] < -1e10) and assert_all(np.isfinite(vals[0]))
+        assert_(vals[1] == 0)
+        assert_all(vals[2] > 1e10) and assert_all(np.isfinite(vals[2]))
+
     def test_integer(self):
         vals = nan_to_num(1)
         assert_all(vals == 1)
diff --git a/numpy/lib/type_check.py b/numpy/lib/type_check.py
index 3bbee0258..a59fe3cc4 100644
--- a/numpy/lib/type_check.py
+++ b/numpy/lib/type_check.py
@@ -315,7 +315,7 @@ def _getmaxmin(t):
     f = getlimits.finfo(t)
     return f.max, f.min
 
-def nan_to_num(x):
+def nan_to_num(x, copy=True):
     """
     Replace nan with zero and inf with finite numbers.
 
@@ -327,6 +327,13 @@ def nan_to_num(x):
     ----------
     x : array_like
         Input data.
+    copy : bool, optional
+        Whether to create a copy of `x` (True) or to replace values
+        in-place (False). The in-place operation only occurs if
+        casting to an array does not require a copy.
+        Default is True.
+
+        .. versionadded:: 1.13
 
     Returns
     -------
@@ -361,7 +368,7 @@ def nan_to_num(x):
             -1.28000000e+002,   1.28000000e+002])
 
     """
-    x = _nx.array(x, subok=True)
+    x = _nx.array(x, subok=True, copy=copy)
     xtype = x.dtype.type
     if not issubclass(xtype, _nx.inexact):
         return x