Why is 08 or 09 in Python invalid?

Question

In the Python interpreter, 08 and 09 seem invalid. Example:

>>> 01
1
>>> 02
2
>>> 03
3
>>> 04
4
>>> 05
5
>>> 06
6
>>> 07
7
>>> 08
  File "<stdin>", line 1
    08
     ^
SyntaxError: invalid token
>>> 09
  File "<stdin>", line 1
    09
     ^
SyntaxError: invalid token

As you can see, only 08 and 09 don't seem to work. Are these special values or something?

It's octal notation. Also a duplicate of a few hundred questions on SO... Please do some effort searching before asking questions, I literally googled `python 08` and was presented with _multiple_ relevant results from SO. — l4mpi, Oct 17 '14 at 11:25
They're octal. http://stackoverflow.com/questions/11620151/what-do-numbers-starting-with-0-mean-in-python — Graham Borland, Oct 17 '14 at 11:25

avi · Accepted Answer · 2014-10-17T11:30:24.857

13

A number with a leading zero is interpreted as octal literal. So 8 and 9 are invalid in octal. Only digits 0 to 7 are valid.

Try in interpreter:

>>> 011
9
>>> 012
10
>>> 013
11

edited Oct 17 '14 at 11:30

answered Oct 17 '14 at 11:25

avi

9,292
11
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84

score 2 · Answer 2 · answered Oct 17 '14 at 11:26

2

If a number starts with 0, it means it's an octal number:

>>> 010
8

answered Oct 17 '14 at 11:26

fredtantini

15,966
8
49
55

score 0 · Answer 3 · answered Oct 17 '14 at 11:29

In Python (along with many other C-origin languages), a leading 0 (and, increasingly a leading 0O) indicate that the number is octal, not decimal. See https://docs.python.org/2/reference/lexical_analysis.html#integer-and-long-integer-literals for details.

For example, and for kicks, see what 010 evaluates to.

Why is 08 or 09 in Python invalid?

3 Answers3

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