Why isn't 0-padding allowed in Python?

Question

I've just noticed 0-padding is not allowed in Python and I was wondering why this choice was made?

For example:

a = 09

doesn't work while

a = 9

does

How's that?!

Thank you very much for your answers!

Answer 1

Python, as many other languages, treat numbers starting with 0 as being in octal notation. 09 is not valid as octal

See chapter 2.4.4 in the python language reference.