BUG/MAINT: Remove special handling of 0d arrays and scalars in interp

These are now handled generically by the underlying C function

This fixes the period argument for 0d arrays.

Now never returns a pure-python scalar, which matches the behaviour of most of numpy.

Rework of b66a200a4a1e98f1955c8a774e4ebfb4588dab5b

2 files changed, 14 insertions, 18 deletions

diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py
index 391c47a06..504280cef 100644
--- a/numpy/lib/function_base.py
+++ b/numpy/lib/function_base.py
@@ -1255,23 +1255,13 @@ def interp(x, xp, fp, left=None, right=None, period=None):
         interp_func = compiled_interp
         input_dtype = np.float64
 
-    if period is None:
-        if isinstance(x, (float, int, number)):
-            return interp_func([x], xp, fp, left, right).item()
-        elif isinstance(x, np.ndarray) and x.ndim == 0:
-            return interp_func([x], xp, fp, left, right).item()
-        else:
-            return interp_func(x, xp, fp, left, right)
-    else:
+    if period is not None:
         if period == 0:
             raise ValueError("period must be a non-zero value")
         period = abs(period)
         left = None
         right = None
-        return_array = True
-        if isinstance(x, (float, int, number)):
-            return_array = False
-            x = [x]
+
         x = np.asarray(x, dtype=np.float64)
         xp = np.asarray(xp, dtype=np.float64)
         fp = np.asarray(fp, dtype=input_dtype)
@@ -1289,10 +1279,7 @@ def interp(x, xp, fp, left=None, right=None, period=None):
         xp = np.concatenate((xp[-1:]-period, xp, xp[0:1]+period))
         fp = np.concatenate((fp[-1:], fp, fp[0:1]))
 
-        if return_array:
-            return interp_func(x, xp, fp, left, right)
-        else:
-            return interp_func(x, xp, fp, left, right).item()
+    return interp_func(x, xp, fp, left, right)
 
 
 def angle(z, deg=0):
diff --git a/numpy/lib/tests/test_function_base.py b/numpy/lib/tests/test_function_base.py
index dc5fe3397..49b450175 100644
--- a/numpy/lib/tests/test_function_base.py
+++ b/numpy/lib/tests/test_function_base.py
@@ -2252,8 +2252,17 @@ class TestInterp(object):
         y = np.linspace(0, 1, 5)
         x0 = np.array(.3)
         assert_almost_equal(np.interp(x0, x, y), x0)
-        x0 = np.array(.3, dtype=object)
-        assert_almost_equal(np.interp(x0, x, y), .3)
+
+        xp = np.array([0, 2, 4])
+        fp = np.array([1, -1, 1])
+
+        actual = np.interp(np.array(1), xp, fp)
+        assert_equal(actual, 0)
+        assert_(isinstance(actual, np.float64))
+
+        actual = np.interp(np.array(4.5), xp, fp, period=4)
+        assert_equal(actual, 0.5)
+        assert_(isinstance(actual, np.float64))
 
     def test_if_len_x_is_small(self):
         xp = np.arange(0, 10, 0.0001)