allows to open read-only zip

Author: Raphael Dussin

zarr/creation.py

@@ -132,7 +132,7 @@ def normalize_store_arg(store, clobber=False, default=dict):
         return default()
     elif isinstance(store, str):
         if store.endswith('.zip'):
-            mode = 'w' if clobber else 'a'
+            mode = 'w' if clobber else 'r'
             return ZipStore(store, mode=mode)
         elif store.endswith('.n5'):
             return N5Store(store)