[Python] Check for None (Null) in Python

If you’ve used other programming languages, you may have learned that an empty object is not the same as an object that does not exist. In this lesson, you’ll learn how to check for None (or Null objects) in Python.

foo = None

if foo is None:
    print("is None")

if foo == None:
    print("also none")

Using ‘is‘ can be better when check is None or not, because ‘is‘ is doing id comparsion:

id(foo) == id(None)

It is much faster check ‘==‘ it does a deep looking for the value.

[Python] Check for None (Null) in Python

原文：http://www.cnblogs.com/Answer1215/p/8012164.html