How to write an octal value in Python 2 & 3

Question

I need to write 0644 (0o644) in Python 2 and 3 compatible way. How to do it? The only ideas I have is to parse this from string or convert into hex or decimal. That's not human-readable. I don't mind slow speed, it's called just once.

Answer 1

Very old python 2 versions (< 2.6) don't accept the octal prefix in 0o644.

If you really need to be compliant with python 2.5 or earlier you can parse an octal string with int

int('644',8)

note that compatibility tricks catching ImportError, NameError, ... exceptions don't work here because you cannot catch the SyntaxError, the parser doesn't let that happen:

# that doesn't work
try:
    x = 0644   # either crashes here
except SyntaxError:
    x = 0o644  # or here
# that doesn't work

Answer 2

0o644 is compatible with both python2 and python3