From 7254888b9ffe1f26ce59600ad31b7d4c9135c13d Mon Sep 17 00:00:00 2001
From: Eric Wieser <wieser.eric@gmail.com>
Date: Fri, 30 Jun 2017 21:58:33 +0100
Subject: ENH: Make duplicated masked constants obvious

---
 numpy/ma/core.py            | 6 +++++-
 numpy/ma/tests/test_core.py | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

(limited to 'numpy/ma')

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index ab4364706..2c62019cd 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -6206,7 +6206,11 @@ class MaskedConstant(MaskedArray):
         return str(masked_print_option._display)
 
     def __repr__(self):
-        return 'masked'
+        if self is masked:
+            return 'masked'
+        else:
+            # something is wrong, make it obvious
+            return object.__repr__(self)
 
     def flatten(self):
         return masked_array([self._data], dtype=float, mask=[True])
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
index 707fcd1de..0a4840d41 100644
--- a/numpy/ma/tests/test_core.py
+++ b/numpy/ma/tests/test_core.py
@@ -4732,6 +4732,12 @@ class TestMaskedConstant(TestCase):
         assert_(not isinstance(m, np.ma.core.MaskedConstant))
         assert_(m is not np.ma.masked)
 
+    def test_repr(self):
+        # copies should not exist, but if they do, it should be obvious that
+        # something is wrong
+        assert_equal(repr(np.ma.masked), 'masked')
+        assert_not_equal(repr(np.ma.masked.copy()), 'masked')
+
 
 def test_masked_array():
     a = np.ma.array([0, 1, 2, 3], mask=[0, 0, 1, 0])
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