From the second link I posted:
octinteger ::= "0" ("o" | "O") octdigit+ | "0" octdigit+
octdigit ::= "0"..."7"
Meaning: numerical literal starting with a
0 and followed by at least one octdigit between
7 inclusive us an octal integer. That is the last part if the first line.
It also could be a capital
o followed by at least one octdigit (middle part of first line).
Or it could start with a zero, followed by an either-cased o-letter and then at least one octdigit, making it an octinteger according the first form of the first line.
print(090). You’ll get an exception…
Meh, typing on the phone gives for funky explanation, in short octal integers start with one or two zeroes or a zero and an o-letter. After tgat start at least one octal digit in the range 0-7 inclusive.