Immutable datatypes(int, float, str, tuple and frozensets)

Frozenset's are immutable and not assignable

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.

Individual characters of strings are not assignable

foo = "bar"
foo[0] = "c" # Error 

Immutable variable value can not be changed once they are created.

Tuple's individual members aren't assignable

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.