Update guess-chunks so that it works with zero dimensions.

zarr/core.py

@@ -265,7 +265,7 @@ def ndim(self):
 
     @property
     def _size(self):
-        return reduce(operator.mul, self._shape)
+        return reduce(operator.mul, self._shape, 1)
 
     @property
     def size(self):
@@ -322,7 +322,7 @@ def cdata_shape(self):
 
     @property
     def _nchunks(self):
-        return reduce(operator.mul, self._cdata_shape)
+        return reduce(operator.mul, self._cdata_shape, 1)
 
     @property
     def nchunks(self):

zarr/tests/test_creation.py

@@ -384,6 +384,22 @@ def test_create():
         create(100, compression=1)
 
 
+def test_create_zero_len():
+
+    # Just test defaults.
+    z = create(0)
+    assert_is_instance(z, Array)
+    eq((0,), z.shape)
+
+    n = z[:]
+    eq(0, len(n))
+
+def test_create_no_dims():
+    ar = np.ndarray(())
+    ar[()] = 100
+    z = array(ar)
+    assert_array_equal(ar, z[:])
+
 def test_compression_args():
 
     z = create(100, compression='zlib', compression_opts=9)

zarr/tests/test_util.py

@@ -183,12 +183,15 @@ def test_guess_chunks():
         (1000, 10000000, 2),
         (10000, 10000, 10000),
         (100000, 100000, 100000),
+        (0,),
+        (0, 0),
+        (1, 2, 0, 4, 5),
     )
     for shape in shapes:
         chunks = guess_chunks(shape, 1)
         assert_is_instance(chunks, tuple)
         eq(len(chunks), len(shape))
-        assert all([c <= s for c, s in zip(chunks, shape)])
+        assert all([c <= max(s, 1) for c, s in zip(chunks, shape)])
 
     # ludicrous itemsize
     chunks = guess_chunks((1000000,), 40000000)

zarr/util.py

@@ -40,7 +40,7 @@ def guess_chunks(shape, typesize):
     """
 
     ndims = len(shape)
-    chunks = np.array(shape, dtype='=f8')
+    chunks = np.maximum(np.array(shape, dtype='=f8'), 1)
 
     # Determine the optimal chunk size in bytes using a PyTables expression.
     # This is kept as a float.
@@ -153,6 +153,11 @@ def normalize_axis_selection(item, l):
             stop = l + stop
         if start < 0 or stop < 0:
             raise IndexError('index out of bounds: %s, %s' % (start, stop))
+
+        # Handle zero-length axis.
+        if start == stop == l == 0:
+            return slice(0, 0)
+
         if start >= l:
             raise IndexError('index out of bounds: %s, %s' % (start, stop))
         if stop > l: