Introduction

In the previous post we finished looking into how boolean types are represented in Python. This short post will show how nulls are represented. We use nulls to indicate the absence of any value in a variable.

None

If you have a C# or Java background then you’ll first guess will be that nulls are assigned by the keyword ‘null’, right? Let’s see:

The compiler won’t like that. Instead, the keyword ‘None’ – strictly with a capital N – is reserved for this purpose. I still like VB.NET’s ‘Nothing’ most but ‘None’ is also more imaginative than a simple ‘null’ :-)

Checking whether a variable is null is performed with the ‘is’ and ‘is not’ operators. You’ll get a warning in the PyCharm IDE if you try to test for None using the equality operator ‘==’:

Instead, write as follows:

res1 will be True and res2 will accordingly be…