None Data Type and Constants in Python

-->None means Nothing or No value associated.

-->If the value is not available, then to handle such type of cases None introduced. It is something like null value in Java.

Example:

def n1(): a=10

print(n1())

None

Constants 

-->Constants concept is not applicable in Python.

-->But it is convention to use only uppercase characters if we don't want to change value.

MAX_VALUE=10

-->It is just convention but we can change the value.