Python Immutable datatypes(int, float, str, tuple and frozensets) is another important parameter used by different programmers . Learn more about it here.
Python Immutable datatypes: Individual characters of strings are not assignable
foo = "bar"
foo = "c" # Error
Immutable variable value can not be changed once they are created.
Section 148.2: Tuple’s individual members aren’t assignable
foo = ("bar", 1, "Hello!",)
foo = 2 # ERROR!!
Second line would return an error since tuple members once created aren’t assignable. Because of tuple’s immutability.
Section 148.3: Frozenset’s are immutable and not assignable
foo = frozenset(["bar", 1, "Hello!"])
foo = 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.