Merge pull request #17058 from BvB93/trim_zeros2

MAINT: Revert boolean casting back to elementwise comparisons in `trim_zeros`

1 files changed, 14 insertions, 8 deletions

diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py
index b530f0aa1..556227c0d 100644
--- a/numpy/lib/function_base.py
+++ b/numpy/lib/function_base.py
@@ -1631,21 +1631,27 @@ def trim_zeros(filt, trim='fb'):
         # Numpy 1.20.0, 2020-07-31
         warning = DeprecationWarning(
             "in the future trim_zeros will require a 1-D array as input "
-            "that is compatible with ndarray.astype(bool)"
+            "that supports elementwise comparisons with zero"
         )
         warning.__cause__ = ex
-        warnings.warn(warning, stacklevel=3)
 
-        # Fall back to the old implementation if an exception is encountered
-        # Note that the same exception may or may not be raised here as well
-        return _trim_zeros_old(filt, trim)
+    # Fall back to the old implementation if an exception is encountered
+    # Note that the same exception may or may not be raised here as well
+    ret = _trim_zeros_old(filt, trim)
+    warnings.warn(warning, stacklevel=3)
+    return ret
 
 
 def _trim_zeros_new(filt, trim='fb'):
     """Newer optimized implementation of ``trim_zeros()``."""
-    arr = np.asanyarray(filt).astype(bool, copy=False)
-
-    if arr.ndim != 1:
+    arr_any = np.asanyarray(filt)
+    arr = arr_any != 0 if arr_any.dtype != bool else arr_any
+
+    if arr is False:
+        # not all dtypes support elementwise comparisons with `0` (e.g. str);
+        # they will return `False` instead
+        raise TypeError('elementwise comparison failed; unsupported data type')
+    elif arr.ndim != 1:
         raise ValueError('trim_zeros requires an array of exactly one dimension')
     elif not len(arr):
         return filt