add asarray

README.rst

@@ -88,6 +88,13 @@ The following involve no memory copies.
     # arr = cuvec.zeros((1337, 42), "float32")
     my_custom_lib.some_cpython_api_func(arr.cuvec)
 
+**CPython API** to **Python**
+
+.. code:: python
+
+    import cuvec, my_custom_lib
+    arr = cuvec.asarray(my_custom_lib.some_cpython_api_func())
+
 **CPython API** to **C++**
 
 .. code:: cpp

cuvec/__init__.py

@@ -21,7 +21,7 @@
     # classes
     'CuVec',
     # functions
-    'dev_sync', 'copy', 'zeros', 'cu_copy', 'cu_zeros',
+    'dev_sync', 'copy', 'zeros', 'asarray', 'cu_copy', 'cu_zeros',
     # data
     'typecodes', 'vec_types'] # yapf: disable
 
@@ -35,7 +35,7 @@
     from warnings import warn
     warn(str(err), UserWarning)
 else:
-    from .helpers import CuVec, copy, zeros
+    from .helpers import CuVec, asarray, copy, zeros
     from .pycuvec import cu_copy, cu_zeros, typecodes, vec_types
 
 # for use in `cmake -DCMAKE_PREFIX_PATH=...`

cuvec/helpers.py

@@ -16,9 +16,9 @@ class CuVec(np.ndarray):
     """
     _Vector_types = tuple(vec_types.values())
 
-    def __new__(cls, arr, cuvec=None):
+    def __new__(cls, arr, raw=None):
         """arr: `cuvec.CuVec`, raw `cuvec.Vector_*`, or `numpy.ndarray`"""
-        if isinstance(arr, CuVec._Vector_types):
+        if isinstance(arr, CuVec._Vector_types) or raw:
             log.debug("wrap raw %s", type(arr))
             obj = np.asarray(arr).view(cls)
             obj.cuvec = arr
@@ -53,3 +53,15 @@ def copy(arr):
     (`cuvec` equivalent of `numpy.copy`).
     """
     return CuVec(cu_copy(arr))
+
+
+def asarray(cuvec):
+    """
+    Returns `CuVec(cuvec, raw=True)`.
+
+    Intended to wrap CPython API functions returning `PyCuVec<T> *` PyObjects.
+    This is needed since `CuVec(cuvec, False)` won't work if
+    `isinstance(cuvec, CuVec) == False` due to external libraries
+    `#include "pycuvec.cuh"` making a distinct type object.
+    """
+    return CuVec(cuvec, raw=True)

tests/test_helpers.py

@@ -49,6 +49,7 @@ def test_CuVec_creation(caplog):
     assert not caplog.record_tuples
     w = cuvec.CuVec(v)
     assert [i[1:] for i in caplog.record_tuples] == [(10, "new view")]
+    assert cuvec.asarray(w.cuvec).cuvec == w.cuvec
 
     caplog.clear()
     assert w[0, 0, 0] == 1