What do numbers starting with 0 mean in python?

Question

When I type small integers with a 0 in front into python, they give weird results. Why is this?

>>> 011
9
>>> 0100
64
>>> 027
23
<         


        

Answer 1

These are octal numbers (base 8, values 0 - 7)

You can convert a decimal number to octal with the oct() function.

In [125]: for i in range(10):
   .....:     print '{:5} {:5}'.format(i, oct(i))
   .....:
    0 0
    1 01
    2 02
    3 03
    4 04
    5 05
    6 06
    7 07
    8 010
    9 011

and convert an octal value to integer with the int() function with the appropriate base (8 in this case):

int(str(17), 8)
Out[129]: 15

The similar set of rules/functions apply for hexadecimal numbers (base 16) using the hex() function.