Invalid Token when using Octal numbers

I'm a beginner in python and I'm trying to use a octal number in my script, but when I try it, it returns me that error:

>>> a = 010
SyntaxError: invalid token (<pyshell#0>, line 1)
>>> 01
SyntaxError: invalid token (<pyshell#1>, line 1)

There's something wrong with my code? I'm using Python3 (and reading a python 2.2 book)