Dictionary values encompass no limitations. They can be any random Python object, moreover standard objects or user-defined objects. Though, same is not true for the keys.
There are two significant points to remember concerning dictionary keys:
(a) More than one entry per key not permitted. Which means no duplicate key is permitted. When duplicate keys occured during assignment, the last assignment wins.
(b) Keys must be unchallengeable. Which means you can use strings, numbers, or tuples as dictionary keys but something similar to [''key''] is not permitted.