Working with attributes

Zarr arrays and groups support custom key/value attributes, which can be useful for storing application-specific metadata. For example:

>>> import zarr
>>> store = zarr.storage.MemoryStore()
>>> root = zarr.create_group(store=store)
>>> root.attrs['foo'] = 'bar'
>>> z = root.create_array(name='zzz', shape=(10000, 10000), dtype='int32')
>>> z.attrs['baz'] = 42
>>> z.attrs['qux'] = [1, 4, 7, 12]
>>> sorted(root.attrs)
['foo']
>>> 'foo' in root.attrs
True
>>> root.attrs['foo']
'bar'
>>> sorted(z.attrs)
['baz', 'qux']
>>> z.attrs['baz']
42
>>> z.attrs['qux']
[1, 4, 7, 12]

Internally Zarr uses JSON to store array attributes, so attribute values must be JSON serializable.