MAINT/BUG: Remove special-casing for 0d arrays, now that indexing with a single boolean is ok

Also fix the test added in gh-4792, which didn't make sense, but passed anyway

1 files changed, 8 insertions, 15 deletions

diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py
index 3a73409fc..573516f3e 100644
--- a/numpy/lib/function_base.py
+++ b/numpy/lib/function_base.py
@@ -1323,21 +1323,15 @@ def piecewise(x, condlist, funclist, *args, **kw):
     """
     x = asanyarray(x)
     n2 = len(funclist)
-    if (isscalar(condlist) or not (isinstance(condlist[0], list) or
-                                   isinstance(condlist[0], ndarray))):
-        if not isscalar(condlist) and x.size == 1 and x.ndim == 0:
-            condlist = [[c] for c in condlist]
-        else:
-            condlist = [condlist]
+
+    # undocumented: single condition is promoted to a list of one condition
+    if isscalar(condlist) or (
+            not isinstance(condlist[0], (list, ndarray)) and x.ndim != 0):
+        condlist = [condlist]
+
     condlist = array(condlist, dtype=bool)
     n = len(condlist)
-    # This is a hack to work around problems with NumPy's
-    #  handling of 0-d arrays and boolean indexing with
-    #  numpy.bool_ scalars
-    zerod = False
-    if x.ndim == 0:
-        x = x[None]
-        zerod = True
+
     if n == n2 - 1:  # compute the "otherwise" condition.
         condelse = ~np.any(condlist, axis=0, keepdims=True)
         condlist = np.concatenate([condlist, condelse], axis=0)
@@ -1352,8 +1346,7 @@ def piecewise(x, condlist, funclist, *args, **kw):
             vals = x[condlist[k]]
             if vals.size > 0:
                 y[condlist[k]] = item(vals, *args, **kw)
-    if zerod:
-        y = y.squeeze()
+
     return y