* Stephen Hansen, on 11.07.2010 21:00:
On 7/11/10 11:45 AM, wheres pythonmonks wrote:
Follow-up:
Is there a way to define compile-time constants in python and have the
bytecode compiler optimize away expressions like:
if is_my_extra_debugging_on: print ...
when "is_my_extra_debugging" is set to false? I'd like to pay no
run-time penalty for such code when extra_debugging is disabled.
Any code wrapped in a __debug__ guard is utterly ommitted if you run
Python with the -O option. That, and asserts go away.
On #2: My point regarding the impossibility of writing the swap
function for ints is to explicitly understand that this isn't
possible, so as not to look for solutions along those lines when
trying to write python code.
Its impossible because Python's calling and namespace semantics simply
don't work like that. There's no references in the traditional sense,
because there's no variables-- boxes that you put values in. There's
just concrete objects. Objects are passed into the function and given
new names; that those objects have names in the enclosing scope is
something you don't know, can't access, and can't manipulate.. even the
objects don't know what names they happen to be called.
Check out http://effbot.org/zone/call-by-object.htm
Oh, I wouldn't give that advice. It's meaningless mumbo-jumbo. Python works like
Java in this respect, that's all; neither Java nor Python support 'swap'.
Of course there are variables, that's why the docs call them variables.
We've had this discussion before and I know from that that it is a religious
issue with a small subset of the Python community, where reason, facts, logic
does not apply and is not even recognized as such. So be it. So I'm not out to
convince you or other of that sub-community, or trying to reason with you folks
on this issue (futile, and generates flames pretty fast), but I do not want
newbies brainwashed into that non-reasoning nonsense pure faith religion.
For what it's worth, I'm sure that the effbot.org author, whose pages are
otherwise quite technically meaningful & useful, in this case, after the flame
war with some Java folks, decided that technical accuracy just wasn't worth it.
So, I believe, he punted, which is an eminently rational choice when one's goals
require acceptance in a society dominated by a religious clique. And just as I'm
not out to engage you in any debate on this issue (futile), neither am I calling
you irrational. Perhaps your choice is the same as that author's.
Cheers,
- Alf
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blog at <url: http://alfps.wordpress.com>
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