BUG: Fix array printing with precision=0.

Values rounding to zero were formatted with negative precision.

2 files changed, 16 insertions, 3 deletions

diff --git a/numpy/core/arrayprint.py b/numpy/core/arrayprint.py
index b05082e9d..cd618d72a 100644
--- a/numpy/core/arrayprint.py
+++ b/numpy/core/arrayprint.py
@@ -626,9 +626,12 @@ class FloatFormat(object):
 
 
 def _digits(x, precision, format):
-    s = format % x
-    z = s.rstrip('0')
-    return precision - len(s) + len(z)
+    if precision > 0:
+        s = format % x
+        z = s.rstrip('0')
+        return precision - len(s) + len(z)
+    else:
+        return 0
 
 
 class IntegerFormat(object):
diff --git a/numpy/core/tests/test_arrayprint.py b/numpy/core/tests/test_arrayprint.py
index 5759a0984..991ead973 100644
--- a/numpy/core/tests/test_arrayprint.py
+++ b/numpy/core/tests/test_arrayprint.py
@@ -129,6 +129,16 @@ class TestPrintOptions:
         np.set_printoptions(precision=4)
         assert_equal(repr(x), "array([ 1.5   ,  0.    ,  1.2346])")
 
+    def test_precision_zero(self):
+        np.set_printoptions(precision=0)
+        for values, string in (
+                ([0.], " 0."), ([.3], " 0."), ([-.3], "-0."), ([.7], " 1."),
+                ([1.5], " 2."), ([-1.5], "-2."), ([-15.34], "-15."),
+                ([100.], " 100."), ([.2, -1, 122.51], "   0.,   -1.,  123."),
+                ([0], "0"), ([-12], "-12"), ([complex(.3, -.7)], " 0.-1.j")):
+            x = np.array(values)
+            assert_equal(repr(x), "array([%s])" % string)
+
     def test_formatter(self):
         x = np.arange(3)
         np.set_printoptions(formatter={'all':lambda x: str(x-1)})