Why does this dictionary definition raise a syntax error? [duplicate]

Answer 1

A number starting with 0 and containing only digits is interpreted in octal. 8 and 9 are not valid octal numbers. If you replace 08 and 09 with 8 and 9, the code will work.

Answer 2

In Python, prefixing a number with a 0 denotes it as being octal. So 08 and 09 give errors because the digits 8 and 9 don't exist in octal. Just get rid of the leading 0 and it'll work.

Answer 3

The number 0 is a prefix on an integer literal indicating that it is an octal number in python.

...which as I accidentally omitted, and as @larsmans so kindly pointed out in his comment, limits the number to containing only the numerals 0 through 7, excluding 8 and 9.

Though, also of note, this is the syntax in Python 2.x - it was changed as of Python 3.0, ostensibly for the exact reason that you came here. PEP 3127 contains the details of the change.

The most relevant bit:

Almost all currently popular computer languages, including C/C++, Java, Perl, and JavaScript, treat a sequence of digits with a leading zero as an octal number. Proponents of treating these numbers as decimal instead have a very valid point -- [...] the entire non-computer world uses decimal numbers almost exclusively.