python optimized mode

Question

Python can run script in optimized mode (-O) that turns off debugs like assert and if I remember also remove docstrings. I have no seen it used really and maybe it is just artifact of the past times. Is it being used? What for?

Why isn't this useless thing being removed in Python 3?

Answer 1

python -O does the following currently:

• completely ignores asserts
• sets the special builtin name __debug__ to False (which by default is True)

and when called as python -OO

• removes docstrings from the code

I don't know why everyone forgets to mention the __debug__ issue; perhaps it is because I'm the only one using it :) An if __debug__ construct creates no bytecode at all when running under -O, and I find that very useful.

Answer 2

It saves a small amount of memory, and a small amount of disk space if you distribute any archive form containing only the .pyo files. (If you use assert a lot, and perhaps with complicated conditions, the savings can be not trivial and can extend to running time too).

So, it's definitely not useless -- and of course it's being used (if you deploy a Python-coded server program to a huge number N of server machines, why ever would you want to waste N * X bytes to keep docstrings which nobody, ever, would anyway be able to access?!). Of course it would be better if it saved even more, but, hey -- waste not, want not!-)

So it's pretty much a no-brainer to keep this functionality (which is in any case trivially simple to provide, you know;-) in Python 3 -- why add even "epsilon" to the latter's adoption difficulties?-)