BUG: bool(dtype) is True

Previously `bool(dtype(...))` would fallback to the default
implementation of `__nonzero__`, which checks if `len(object) > 0`.
Since `dtype` objects implement `__len__` as the number of record
fields, `bool` of scalar dtypes like `bool(dtype('i8'))` would evaluate
as `False`. This fixes that by implementing `__nonzero__` to always
return True.

Fixes #6294.

1 files changed, 9 insertions, 0 deletions

diff --git a/doc/release/1.13.0-notes.rst b/doc/release/1.13.0-notes.rst
index b54e48ba7..69e2a6b5b 100644
--- a/doc/release/1.13.0-notes.rst
+++ b/doc/release/1.13.0-notes.rst
@@ -56,6 +56,15 @@ See Changes section for more detail.
 * ``array == None`` and ``array != None`` do element-wise comparison.
 * ``np.equal, np.not_equal``, object identity doesn't override comparison result.
 
+dtypes are now always true
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Previously ``bool(dtype)`` would fall back to the default python
+implementation, which checked if ``len(dtype) > 0``. Since ``dtype`` objects
+implement ``__len__`` as the number of record fields, ``bool`` of scalar dtypes
+would evaluate to ``False``, which was unintuitive. Now ``bool(dtype) == True``
+for all dtypes.
+
 
 C API
 ~~~~~