Warning: this post contains arcane knowledge.
Steve Holden wrote:
> praba kar wrote:
>> Python 2.3 creates byte code with *.pyc
>> extention. But Python 2.4 creates bytes code with
>> *.pyo. Is there any difference between *.pyc
>> and *.pyo?.
>>
> Yes. The .pyo files are optimized by removing certain features that
> aren't essential to execution (things like doc strings).
The -O option defines __debug__ to be False, and (as a side-effect)
ignores assert statements in the code used. The -OO option does
everything the -O option does, while also removing things like doc
strings. Both -O and -OO produce .pyo files, so having made things
with -OO, even using -O you will not see the doc strings in those
modules.
Here is a weird python program called opdemo.py to show these effects:
Call it opdemo.py
==================================
import sys
def function():
'''doc strings kept'''
try:
assert 4 == 5
print '%s: assert skipped (__debug__ = %s)' % (
__name__, __debug__)
except AssertError:
print '%s: assert checked (__debug__ = %s)' % (
__name__, __debug__)
docstring = function.__doc__ or 'No doc strings'
print sys.version
print '%s: __debug__ = %s; %s' % (__name__, __debug__, docstring)
print __file__
function()
if __name__ == '__main__':
print '============='
import opdemo
print opdemo.__name__, opdemo.docstring, opdemo.__file__
opdemo.function()
==================================
Now that you have this, you can run:
python opdemo.py
and then
python opdemo.py
To see how you can tell if you are running post-compiled.
If you run
python -OO opdemo.py
and then
python -O opdemo.py
You will see it looks like -O also removes docstrings.
However if you delete opdemo.py and run
python -O opdemo.py
and then
python -O opdemo.py
You will see the docstrings are in fact there for -O.
Of course, for all of this you will have to think a lot about
exactly what code is being executed. A help to figuring this out
is to remember that if you import a module you get a new and
different copy of the module from the main program.
--Scott David Daniels
[EMAIL PROTECTED]
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