IDLE processes numerical input in a weird way (python 2.6)

Question

If you simply type an integer after the >>> prompt they give you in the IDLE interpreter, most of the time it'll simply bounce the number back at you.

>>> 3
3
>>> 8
8
>>> 10
10

Start the nubmer off with a 0 however, and some interesting errors happen.

>>> 010
8
>>> 020
16

Answer 1

In Python 2, an integer literal starting with 0 is considered octal, i.e. in base 8. And obviously, 10 oct == 8 dec (or generally, 10 in base b == b base 10). Likewise, 12 oct == 10 dec, and so on.