foo = ("bar", 1, "Hello!",)
foo[1] = 2 # ERROR!!
Second line would return an error since tuple members once created aren't assignable.
Because of tuple's immutability.
foo = frozenset(["bar", 1, "Hello!"])
foo[2] = 7 # ERROR
foo.add(3) # ERROR
Second line would return an error since frozenset members once created aren't assignable.
Third line would return error as frozensets do not support functions that can manipulate members.