Allow disabling filling of missing chunks

zarr/core.py

@@ -93,6 +93,7 @@ class Array(object):
     set_mask_selection
     get_coordinate_selection
     set_coordinate_selection
+    set_options
     digest
     hexdigest
     resize
@@ -710,6 +711,8 @@ def _get_basic_selection_zd(self, selection, out=None, fields=None):
             cdata = self.chunk_store[ckey]
 
         except KeyError:
+            if not self._fill_missing_chunk:
+                raise
             # chunk not initialized
             chunk = np.zeros((), dtype=self._dtype)
             if self._fill_value is not None:
@@ -1376,6 +1379,18 @@ def set_coordinate_selection(self, selection, value, fields=None):
 
         self._set_selection(indexer, value, fields=fields)
 
+    def set_options(self, fill_missing_chunk=True):
+        """Set options.
+
+        Parameters
+        ----------
+        fill_missing_chunk : bool
+            Whether Zarr is supposed to fill missing chunks.  Defaults to True.
+
+        """
+
+        self._fill_missing_chunk = fill_missing_chunk
+
     def set_mask_selection(self, selection, value, fields=None):
         """Modify a selection of individual items, by providing a Boolean array of the
         same shape as the array against which the selection is being made, where True
@@ -1472,6 +1487,8 @@ def _set_basic_selection_zd(self, selection, value, fields=None):
             cdata = self.chunk_store[ckey]
 
         except KeyError:
+            if not self._fill_missing_chunk:
+                raise
             # chunk not initialized
             chunk = np.zeros((), dtype=self._dtype)
             if self._fill_value is not None:
@@ -1579,6 +1596,8 @@ def _chunk_getitem(self, chunk_coords, chunk_selection, out, out_selection,
             cdata = self.chunk_store[ckey]
 
         except KeyError:
+            if not self._fill_missing_chunk:
+                raise
             # chunk not initialized
             if self._fill_value is not None:
                 if fields:
@@ -1692,6 +1711,9 @@ def _chunk_setitem_nosync(self, chunk_coords, chunk_selection, value, fields=Non
 
             except KeyError:
 
+                if not self._fill_missing_chunk:
+                    raise
+
                 # chunk not initialized
                 if self._fill_value is not None:
                     chunk = np.empty(self._chunks, dtype=self._dtype, order=self._order)