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Python 3.4 interpreter fail to parse a integer that has zero padding, whereas python 2.7 works properly.
Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> int(001)
1
>>> 
Python 3.4.0 (default, Apr 11 2014, 13:05:11) 
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> int(001)
 File "<stdin>", line 1
 int(001)
 ^
SyntaxError: invalid token
>>>

This is not a bug, it's a deliberate change.
Python 2.x doesn't "work correctly"; what you have there is an octal literal, not a 0-padded base-10 integer. Try 008 or 011 and be surprised that python 2 is "broken" and you'll see why this syntax was removed.

Thanks for the response, but in my case, 001 is not an octal literal, is a base-10 zero padded comming from the parsing of a ip string like 111.000.222.333 , where numbers are all integers in base-10.
The solution for parsing that seams to cast 000 as string and then using int('000', base=10).

> is a base-10 zero padded comming from the parsing of a ip string
If you're parsing an ip string, how do you end up with a 000 *literal*? The SyntaxError only applies to literals in Python code; it doesn't affect conversion from strings to integers. So you don't need the "base=10" keyword: the following works in both Python 2 and Python 3.
>>> int("000")
0
>>> int("0019")
19