[Python-Dev] #12982: Should -O be required to *read* .pyo files?

[Ethan Furman]

Alexandre Zani wrote:
> On Tue, Jun 12, 2012 at 11:41 AM, Ethan Furman <ethan at stoneleaf.us> wrote:
>> Terry Reedy wrote:
>>> http://bugs.python.org/issue12982
>>>
>>> Currently, cpython requires the -O flag to *read* .pyo files as well as
>>> the write them. This is a nuisance to people who receive them from others,
>>> without the source. The originator of the issue quotes the following from
>>> the doc (without giving the location).
>>>
>>> "It is possible to have a file called spam.pyc (or spam.pyo when -O is
>>> used) without a file spam.py for the same module. This can be used to
>>> distribute a library of Python code in a form that is moderately hard to
>>> reverse engineer."
>>>
>>> There is no warning that .pyo files are viral, in a sense. The user has to
>>> use -O, which is a) a nuisance to remember if he has multiple scripts and
>>> some need it and some not, and b) makes his own .py files used with .pyo
>>> imports cached as .pyo, without docstrings, like it or not.
>>>
>>> Currently, the easiest workaround is to rename .pyo to .pyc and all seems
>>> to work fine, even with a mixture of true .pyc and renamed .pyo files. (The
>>> same is true with the -O flag and no renaming.) This suggests that there is
>>> no current reason for the restriction in that the *execution* of bytecode is
>>> not affected by the -O flag. (Another workaround might be a custom importer
>>> -- but this is not trivial, apparently.)
>>>
>>> So is the import restriction either an accident or obsolete holdover? If
>>> so, can removing it be treated as a bugfix and put into current releases, or
>>> should it be treated as an enhancement only for a future release?
>>>
>>> Or is the restriction an intentional reservation of the possibility of
>>> making *execution* depend on the flag? Which would mean that the restriction
>>> should be kept and only the doc changed?
>>
>> I have no history so cannot say what was supposed to happen, but my $0.02
>> would be that if -O is *not* specified then we should try to read .pyc, then
>> .pyo, and finally .py.  In other words, I vote for -O being a write flag,
>> not a read flag.
> 
> What if I change .py?

Well, the case in question is that there is no .py available.

But if it were available, and you changed it, then it would and should 
work just like it does now -- if .py is newer, compile it; if -O was 
specified, compile it optimized;  now run the compiled code.

~Ethan~