 <p>You can't, because it's an invalid concept. Datastore entities are stored as a set of key/value pairs. When you store a list of any kind, it's internally represented as multiple pairs with the same key and different values, rather than one key with a list of values.</p> <p>Storing an empty list is thus equivalent to not storing anything at all. You just have zero instances of that property inside your entity. If you want to represent an empty list, leave the property unset. If you need to differentiate between an unset property and the concept of an empty list, fill the dynamic property with some other non-empty value, like <code>None</code> or <code>False</code>.</p>