On Mon, 23 Jan 2012 20:50:11 +, Andrea Crotti wrote:
> while 1 works because the 1 is converted to boolean automatically, but
> why not just writing a boolean
> in the first place?
You have misunderstood Python's truth model. It is similar to languages
like Javascript and PHP, where EVERY ob
在 2012年1月24日星期二UTC+8上午4时50分11秒，Andrea Crotti写道：
> On 01/23/2012 06:05 PM, Evan Driscoll wrote:
> >
> > To play devil's advocate for a moment, if you have the choice between
> > two ways of writing something, A and B, where both are basically the
> > same in terms of difficulty to write, difficult
On 01/23/2012 06:05 PM, Evan Driscoll wrote:
To play devil's advocate for a moment, if you have the choice between
two ways of writing something, A and B, where both are basically the
same in terms of difficulty to write, difficulty to maintain, and
difficulty to understand, but A is faster t
Il 23 gennaio 2012 20:12, Erik Max Francis ha scritto:
> Giampaolo Rodolà wrote:
>>
>> Il 21 gennaio 2012 22:13, Erik Max Francis ha scritto:
>>>
>>> The real reason people still use the `while 1` construct, I would
>>> imagine,
>>>
>>> is just inertia or habit, rather than a conscious, defensive
Giampaolo Rodolà wrote:
Il 21 gennaio 2012 22:13, Erik Max Francis ha scritto:
The real reason people still use the `while 1` construct, I would imagine,
is just inertia or habit, rather than a conscious, defensive decision. If
it's the latter, it's a case of being _way_ too defensive.
It's
On 01/23/2012 11:39 AM, Ian Kelly wrote:
"We should forget about small efficiencies, say about 97% of the time:
premature optimization is the root of all evil"
-- Donald Knuth
To play devil's advocate for a moment, if you have the choice between
two ways of writing something, A and B, where bo
On 01/23/2012 08:28 AM, Hrvoje Niksic wrote:
Dave Angel writes:
I do something similar when there's a portion of code that should
never be reached:
assert("reason why I cannot get here")
Shouldn't that be assert False, "reason why I cannot get here"?
You caught me in a typo. If it's in pyth
On Mon, Jan 23, 2012 at 9:41 AM, Giampaolo Rodolà wrote:
>
> Il 21 gennaio 2012 22:13, Erik Max Francis ha scritto:
> > The real reason people still use the `while 1` construct, I would imagine,
> > is just inertia or habit, rather than a conscious, defensive decision. If
> > it's the latter, it
Il 21 gennaio 2012 22:13, Erik Max Francis ha scritto:
> The real reason people still use the `while 1` construct, I would imagine,
> is just inertia or habit, rather than a conscious, defensive decision. If
> it's the latter, it's a case of being _way_ too defensive.
It's also because while 1 i
On 2012-01-21, Erik Max Francis wrote:
> Chris Angelico wrote:
>> On Sun, Jan 22, 2012 at 12:47 AM, Andrea Crotti
>> wrote:
>>> So I tried to do the following, and the result is surprising. For what
>>> I can see it looks like the interpreter can optimize away the 1 boolean
>>> conversion while
Dave Angel writes:
> I do something similar when there's a portion of code that should
> never be reached:
>
> assert("reason why I cannot get here")
Shouldn't that be assert False, "reason why I cannot get here"?
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On 01/22/2012 10:55 PM, alex23 wrote:
On Jan 23, 2:05 am, Dan Sommers wrote:
As per a now-ancient suggestion on this mailing list (I believe it was by
Tim Peters), I've also been known to use a non-empty, literal Python
string as a self-documenting, forever-True value in the typical loop-and-a-
On Jan 23, 2:05 am, Dan Sommers wrote:
> As per a now-ancient suggestion on this mailing list (I believe it was by
> Tim Peters), I've also been known to use a non-empty, literal Python
> string as a self-documenting, forever-True value in the typical loop-and-a-
> half cnstruct:
>
> while "th
On 22/01/2012 16:05, Dan Sommers wrote:
On Sun, 22 Jan 2012 05:25:25 +, Steven D'Aprano wrote:
Or they've been writing Python code since before version 2.2 when True
and False were introduced, and so they are used to the "while 1" idiom
and never lost the habit.
That would be me.
As p
On Sun, 22 Jan 2012 05:25:25 +, Steven D'Aprano wrote:
> Or they've been writing Python code since before version 2.2 when True
> and False were introduced, and so they are used to the "while 1" idiom
> and never lost the habit.
That would be me.
As per a now-ancient suggestion on this maili
On Sun, 22 Jan 2012 09:13:23 +1100, Chris Angelico wrote:
> On Sun, Jan 22, 2012 at 8:13 AM, Erik Max Francis
> wrote:
>> Why this should concern anyone, I don't know; someone who's rebound
>> `True` or `False` to evaluate to something other than true and false,
>> respectively, is only doing so
On Sun, Jan 22, 2012 at 8:13 AM, Erik Max Francis wrote:
> Why this should concern anyone, I don't know; someone who's rebound `True`
> or `False` to evaluate to something other than true and false, respectively,
> is only doing so to be difficult (or very foolish). One of the principles
> of Pyt
Andrea Crotti wrote:
I see sometimes in other people code "while 1" instead of "while True".
I think using True is more pythonic, but I wanted to check if there is
any difference in practice.
No (with the exception of `True` and `False` being rebinable in Python
2). The idiomatic `while 1` no
Chris Angelico wrote:
On Sun, Jan 22, 2012 at 12:47 AM, Andrea Crotti
wrote:
So I tried to do the following, and the result is surprising. For what
I can see it looks like the interpreter can optimize away the 1 boolean
conversion while it doesn't with the True, the opposite of what I
supposed
Probably because of the fact it is possible to set True equal to False and
consequently then invalidate loop logic as presented below:
True = False
while True:
...
On the other hand `1' will always be evaluated as a constant.
Don't know, just guessing.
Matteo
On Jan/21, Andrea
On Sun, Jan 22, 2012 at 12:47 AM, Andrea Crotti
wrote:
> So I tried to do the following, and the result is surprising. For what
> I can see it looks like the interpreter can optimize away the 1 boolean
> conversion while it doesn't with the True, the opposite of what I
> supposed.
>
> Anyone can
Actually there was the same question here (sorry should have looked before)
http://stackoverflow.com/questions/3815359/while-1-vs-for-whiletrue-why-is-there-a-difference
And I think the main reason is that 1 is a constant while True is not
such and can be reassigned.
--
http://mail.python.org/mai
I see sometimes in other people code "while 1" instead of "while True".
I think using True is more pythonic, but I wanted to check if there is
any difference in practice.
So I tried to do the following, and the result is surprising. For what
I can see it looks like the interpreter can optimize a
hehehehehehe...
On 17/12/2010 2.01, Steven D'Aprano wrote:
On Thu, 16 Dec 2010 23:34:21 +, BartC wrote:
In terms of a more realistic function (admittedly still a little
contrived, as the loop would be written differently), I tried this:
def p2(n):
p=1
while True:
if n<=p: retur
On Thu, 16 Dec 2010 23:34:21 +, BartC wrote:
> In terms of a more realistic function (admittedly still a little
> contrived, as the loop would be written differently), I tried this:
>
> def p2(n):
> p=1
> while True:
> if n<=p: return p
> p<<=1
> return 0
>
> for i in xrange(10
On Dec 16, 4:34 pm, "BartC" wrote:
> def p2(n):
> p=1
> whileTrue:
> if n<=p: return p
> p<<=1
> return 0
>
> for i in xrange(100):
> x=p2(i)
>
> p2() calculates the smallest power of 2 >= it's operand.
def p2(n):
return 1 << n.bit_length()
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http://mail.python.org/mailman/
"Steve Holden" wrote in message
news:mailman.54.1292502247.6505.python-l...@python.org...
On 12/16/2010 5:44 AM, BartC wrote:
One these is 30% faster than the other. That's an appreciable
difference, which you can't really just dismiss.
shol...@lifeboy ~
$ python -m timeit -- "i = 1" "whi
Arnaud Delobelle wrote:
Ethan Furman writes:
...I timed exec vs function, and found the function style to be about
200% faster...
So it finished before it started?
Hmmm
Let me check my calculator...
.
.
.
Ah! Okay, that was 200x faster. :) I think -- it was a few months ago
no
On 12/16/2010 7:23 AM, Steve Holden wrote:
On 12/16/2010 5:44 AM, BartC wrote:
One these is 30% faster than the other. That's an appreciable
difference, which you can't really just dismiss.
And you can't tell what the overall effect on a program will be: perhaps
the loop will be in a library
Ethan Furman writes:
> ...I timed exec vs function, and found the function style to be about
> 200% faster...
So it finished before it started?
--
Arnaud
--
http://mail.python.org/mailman/listinfo/python-list
BartC wrote:
"Steve Holden" wrote in message
news:mailman.462.1292214062.2649.python-l...@python.org...
On 12/12/2010 2:32 PM, Christian Heimes wrote:
Am 12.12.2010 19:31, schrieb Steve Holden:
$ python -m timeit -n20 -- "i = 0" "while 1:" "i+=1" "if i ==
100: break"
20 loops, best
On 12/16/2010 5:44 AM, BartC wrote:
>> On 12/12/2010 2:32 PM, Christian Heimes wrote:
>>> Am 12.12.2010 19:31, schrieb Steve Holden:
>>> $ python -m timeit -n20 -- "i = 0" "while 1:" "i+=1" "if i ==
>>> 100: break"
>>> 20 loops, best of 3: 89.7 msec per loop
>>> $ python -m timeit -n20
"Steve Holden" wrote in message
news:mailman.462.1292214062.2649.python-l...@python.org...
On 12/12/2010 2:32 PM, Christian Heimes wrote:
Am 12.12.2010 19:31, schrieb Steve Holden:
$ python -m timeit -n20 -- "i = 0" "while 1:" "i+=1" "if i ==
100: break"
20 loops, best of 3: 89.7 ms
On 12/15/2010 8:10 AM, Hans-Peter Jansen wrote:
> On Tuesday 14 December 2010, 21:38:47 Arnaud Delobelle wrote:
>> Christian Heimes writes:
>> [...]
>>
>>> Tres Seavers once told me a joke like this:
>>>
>>>True = not not "Who's at the door?" # say it out loud!
>>>
>>> This was back in the old
On Tuesday 14 December 2010, 21:38:47 Arnaud Delobelle wrote:
> Christian Heimes writes:
> [...]
>
> > Tres Seavers once told me a joke like this:
> >
> >True = not not "Who's at the door?" # say it out loud!
> >
> > This was back in the old days of Zope 2.5 and Python 2.1, which
> > didn't ha
On 14 déc, 21:38, Arnaud Delobelle wrote:
> I almost used:
>
> True = "to be" or not "to be" # that is the question
KEYBOARD !-)
--
http://mail.python.org/mailman/listinfo/python-list
Christian Heimes writes:
[...]
> Tres Seavers once told me a joke like this:
>
>True = not not "Who's at the door?" # say it out loud!
>
> This was back in the old days of Zope 2.5 and Python 2.1, which didn't
> have True and False.
I almost used:
True = "to be" or not "to be" # that is
Am 14.12.2010 17:52, schrieb Arnaud Delobelle:
> You also need to initialise False to False for it to be really
> robust. So something like this will do.
>
> True = not 0
> False = not True
> while True:
> ...
> True = False
Tres Seavers once told me a joke like this:
Gregory Ewing writes:
> Steven D'Aprano wrote:
>
>while True:
>>
>> ... print "Looping"
>> ... True = 0
>
> Just remember that if you use that inside a function, you'll
> have to initialise True to True before... er, wait a moment,
> that won't work... ah, I know:
>
> def f(true = T
Am 14.12.2010 11:33, schrieb Hans-Peter Jansen:
> On Tuesday 14 December 2010, 10:19:04 Gregory Ewing wrote:
>> Steven D'Aprano wrote:
>> while True:
>>>
>>> ... print "Looping"
>>> ... True = 0
>>
>> Just remember that if you use that inside a function, you'll
>> have to initialise True to Tru
On Tuesday 14 December 2010, 10:19:04 Gregory Ewing wrote:
> Steven D'Aprano wrote:
> while True:
> >
> > ... print "Looping"
> > ... True = 0
>
> Just remember that if you use that inside a function, you'll
> have to initialise True to True before... er, wait a moment,
> that won't wor
Steven D'Aprano wrote:
while True:
... print "Looping"
... True = 0
Just remember that if you use that inside a function, you'll
have to initialise True to True before... er, wait a moment,
that won't work... ah, I know:
def f(true = True):
True = true
while True:
..
On 2010-12-12, Steven D'Aprano wrote:
> With the "while True" idiom in Python 2.x, you can easily exit out of an
> infinite loop without using break:
>
while True:
> ... print "Looping"
> ... True = 0
> ...
> Looping
while True: # Execute an infinite loop in 0 seconds.
>
Paul Rubin wrote:
Steven D'Aprano writes:
I'm actually quite fond of the look of "while 1:", and sometimes use it,
not because it's faster, but just because I like it.
for v in itertools.repeat(True):
...
;-)
while '__For_ever___' not in ['nit-picking']:
:)
JM
--
http
Steven D'Aprano writes:
> I'm actually quite fond of the look of "while 1:", and sometimes use it,
> not because it's faster, but just because I like it.
for v in itertools.repeat(True):
...
;-)
--
http://mail.python.org/mailman/listinfo/python-list
On Sun, 12 Dec 2010 23:20:40 -0500, Steve Holden wrote:
> On 12/12/2010 2:32 PM, Christian Heimes wrote:
[...]
>> No argue with that! I was merely making a point that "while 1" executes
>> different byte code than "while True". Readability is important but
>> sometimes speed is of the essence. "wh
On 12/12/2010 2:32 PM, Christian Heimes wrote:
> Am 12.12.2010 19:31, schrieb Steve Holden:
>> > Would you care to quantify how much CPU time that optimization will
>> > typically save for a loop of fair magnitude (say, a billion iterations)?
> The difference is minimal but measurable for very tigh
On Sun, 12 Dec 2010 16:33:41 +0100, Krister Svanlund wrote:
> On Sun, Dec 12, 2010 at 3:14 PM, Max Countryman wrote:
>> I'm sure this has been brought up many times, but a quick Googling
>> didn't yield the decisive results I was hoping for, so I apologize if
>> this has already been addressed in
>> Python is designed to provide readable code. Writing
>>
>> while True:
>> ...
>>
>> is much more legible than its pre-True couterpart
>>
>> while 1:
>> ...
>
> No argue with that!
I actually want to argue with that: I find "while 1" more legible.
That's probably because
Am 12.12.2010 19:31, schrieb Steve Holden:
> Would you care to quantify how much CPU time that optimization will
> typically save for a loop of fair magnitude (say, a billion iterations)?
The difference is minimal but measurable for very tight loops.
$ python -m timeit -n20 -- "i = 0" "while 1:"
On 12/12/2010 10:30 AM, Christian Heimes wrote:
> Am 12.12.2010 15:14, schrieb Max Countryman:
>> I'm sure this has been brought up many times, but a quick Googling didn't
>> yield the decisive results I was hoping for, so I apologize if this has
>> already been addressed in great detail somewher
On Sun, Dec 12, 2010 at 3:14 PM, Max Countryman wrote:
> I'm sure this has been brought up many times, but a quick Googling didn't
> yield the decisive results I was hoping for, so I apologize if this has
> already been addressed in great detail somewhere else.
>
> I am wondering what the ration
Am 12.12.2010 15:14, schrieb Max Countryman:
> I'm sure this has been brought up many times, but a quick Googling didn't
> yield the decisive results I was hoping for, so I apologize if this has
> already been addressed in great detail somewhere else.
>
> I am wondering what the rationale is beh
I'm sure this has been brought up many times, but a quick Googling didn't yield
the decisive results I was hoping for, so I apologize if this has already been
addressed in great detail somewhere else.
I am wondering what the rationale is behind preferring while True over while 1?
For me, it see
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