If the number of entities in your datastore is not very large, then you can use the below approach:
1, Use yourquery = entitykind.query() to fetch all entities
2, Use yourquery.count() to get the number of entities
3, Use a random number generator to create a random number within the above count value
4, Use a for loop to iterate through the entities returned by
yourquery.fetch()
and then when the number of times the loop has been executed equals the above random number, use the particular entity in your webapp
