>>> a = 255 # or another number from -5 to 256
>>> b = 999 # or another number outside -5 to 256
>>> a is 255
True
>>> b is 999
False

$ python3.7 -VV
Python 3.7.3 (default, Mar 26 2019, 01:59:45)
[GCC 5.4.0 20160609]

Python 3.7.3 (default, Mar 26 2019, 01:59:45)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> a = 255
>>> b = 999
>>> print("255:", a is 255)
255: True
>>> print("999:", b is 999)
999: False

#!/usr/bin/env python3.7
# -*- coding: utf-8 -*-

a = 255
b = 999
print("255:", a is 255)
print("999:", b is 999)

$ python3.7 test.py
255: True
999: True