🌐 Mailman 3 August 2007 - Python-list - python.org

Re: How to use os.putenv() ?
by T Aug. 30, 2007

Aug. 30, 2007

Thank you everyone!

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Re: subclassing Python types
by Arnaud Delobelle Aug. 30, 2007

Aug. 30, 2007

On Aug 30, 8:44 pm, Robert Kern <robert.k...(a)gmail.com> wrote: > zzbba...(a)aol.com wrote: > > So it's: > > class MyString(str): > > def __init__(self,strInput): > > self = strInput > > That doesn't quite work. Assigning to "self" only reassigns the name inside the > function. It does not replace the object. > > Instead, call the .__init__() method on str. That won't do much as strings are immutable objects... As pointed out by Steve Holden and me, str.__new__ is the way. -- Arnaud

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Re: Is LOAD_GLOBAL really that slow?
by Rhamphoryncus Aug. 30, 2007

Aug. 30, 2007

On Aug 30, 12:04 pm, "Chris Mellon" <arka...(a)gmail.com> wrote: > On 8/30/07, Rhamphoryncus <rha...(a)gmail.com> wrote: > > > On Aug 29, 8:33 pm, Carsten Haese <cars...(a)uniqsys.com> wrote: > > > On Wed, 2007-08-29 at 19:23 -0600, Adam Olsen wrote: > > > There is no loop overhead here, and after subtracting the function call > > > overhead, I get 31 nanoseconds per local lookup and 63 nanoseconds per > > > global lookup, so local lookups are just about twice as fast as global > > > lookups. > > __builtins__ lookups are an extra dict lookup slower than just global > variables, too. Don't forget those. Heh right, I forgot that. That's what my benchmark was actually testing. > > > True, whether this difference is significant does depend on how many > > > name lookups your code makes and how much else it's doing, but if you're > > > doing a lot of number crunching and not a lot of I/O, the difference > > > might be significant. Also, even if using local names is only slightly > > > faster than using globals, it's still not slower, and the resulting code > > > is still more readable and more maintainable. Using locals is a win-win > > > scenario. > > > You get very small speed gains (assuming your code is doing anything > > significant), for a lot of effort (trying out different options, > > seeing if they're actually faster on different boxes.) The > > readability cost is there, even if it is smaller than many of the > > other obfuscations people attempt. If the speed gains were really > > that important you should rewrite in C, where you'd get far greater > > speed gains. > > I've doubled the speed of a processing loop by moving globals lookups > out of the loop. Rewriting in C would have taken at least a day, even > with Pyrex, localizing the lookup took about 2 minutes. I'm guessing that was due to deep voodoo involving your processor's pipeline, branch prediction, caching, etc. I'd be interested in seeing small examples of it though. > > So it only seems worthwhile when you really, *really* need to get a > > slight speedup on your box, you don't need to get any more speedup > > than that, and C is not an option. > > It's not a huge optimization, but it's really easy to write if you > don't mind adding fake kwargs to your functions. Just for the heck of > it I also wrote a decorator that will re-write the bytecode so that > any global that can be looked up at function definition will be > re-written as a local (actually with LOAD_CONST). You can see it athttp://code.google.com/p/wxpsvg/wiki/GlobalsOptimization. Disclaimer: > While I've tested it with a variety of functions and it's never broken > anything, I've never actually used this for anything except an > intellectual exercise. Use at your own risk. Doubling the throughput while doing *real work* is definitely more significant than maybe-or-maybe-not-quite-doubling without any real work. -- Adam Olsen, aka Rhamphoryncus

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Re: gc.garbage
by 7stud Aug. 30, 2007

Aug. 30, 2007

On Aug 30, 12:36 pm, "Chris Mellon" <arka...(a)gmail.com> wrote: > On 8/30/07, 7stud <bbxx789_0...(a)yahoo.com> wrote: > > > On Aug 30, 3:50 am, "Martin v. L�wis" <mar...(a)v.loewis.de> wrote: > > > > gc.set_debug(gc.DEBUG_LEAK) > > > > print gc.garbage > > > > > --output:-- > > > > [] > > > > gc: uncollectable <Dog 0x56e10> > > > > gc: uncollectable <Cat 0x56e30> > > > > gc: uncollectable <dict 0x58270> > > > > gc: uncollectable <dict 0x43e40> > > > > gc.garbage is filled only after these messages > > > are printed, not before. You need to add an explicit > > > call to gc.collect() if you want to see what > > > uncollectable garbage you have. > > > > Regards, > > > Martin > > > Hi, > > > Thanks for the response. I had a cut and paste error in my reply, so > > here it is again with the corrections... > > > Now, if I run the code: > > > ------------ > > import gc > > > class Cat(object): > > def __del__(): > > pass > > > class Dog(object): > > def __del__(): > > pass > > > def some_func(): > > the_dog = Dog() > > the_cat = Cat() > > the_dog.cat = the_cat > > the_cat.dog = the_dog > > > some_func() > > > gc.set_debug(gc.DEBUG_LEAK) > > gc.collect() > > print gc.garbage > > ----------- > > > I get this output: > > > ---------- > > gc: uncollectable <Dog 0x56e10> > > gc: uncollectable <Cat 0x56e30> > > gc: uncollectable <dict 0x58300> > > gc: uncollectable <dict 0x43e40> > > [<__main__.Dog object at 0x56e10>, <__main__.Cat object at 0x56e30>, > > {'cat': <__main__.Cat object at 0x56e30>}, {'dog': <__main__.Dog > > object at 0x56e10>}] > > ----------- > > > Why are there two entries in the list for each uncollectable > > object(same addresses)? Also, I haven't bound the names "cat" or > > "dog" anywhere in my program. What do those names mean in the list? > > Read your output carefully! > > gc.garbage is a list of objects. The objects are printed just as they > would be anywhere else in Python. You've got the dog object, the cat > object, and the __dict__ of each instance. > > Ah. I missed the braces inside the list, but I still don't understand where the names "cat" and "dog" come from. > DEBUG_SAVEALL is set, then all unreachable objects will be added to > this list rather than freed." What is the definition of an "unreachable object"? If I add the following: ----- y = Cat() del y ----- That object doesn't make it into gc.garbage.

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Python weather application
by seancron Aug. 30, 2007

Aug. 30, 2007

Does anybody have any suggestions for getting started on desigining a desktop weather application in Python? I've been looking for access to weather data and while I have found several including the weather.com service I've decided to use the Yahoo! Rss Weather feed since it doesn't have a license like the weather.com service does. However one problem I have with it is that it only accepts zip codes or locations ids. So if a user was to enter the name of the city instead of those two there would be an error. I could make it so they could only enter in the location code or zip code but I would really prefer to have it be automatically corrected. Does anyone have ideas on how to go about this or have an other suggestions? Thanks, Sean

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subclassing Python types
by zzbbaadd＠aol.com Aug. 30, 2007

Aug. 30, 2007

I have read that you can derive from the base classes such as str, list, dict. I guess this would look like: def MyString(str): def MyList(list): def MyDict(dict): How do you access the data that is contained in the super class?

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Trouble using sys.settrace
by tleeuwenburg＠gmail.com Aug. 30, 2007

Aug. 30, 2007

The code below produces no output. I would expect to see: tracing... tracing... tracing... tracing... tracing... I was wondering if anyone had any experience with this. ================================= import sys def mytrace(frame, event, arg): print "tracing..." sys.settrace(mytrace) def foo(): for i in range(5): print i foo()

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pure python for sms
by Gerardo Herzig Aug. 30, 2007

Aug. 30, 2007

Hi dudes. Im looking for a python implementation for sending sms to a cell phone. I was try using some free pages, but i want to use a python. Do i need a cellphone conected to my machine? Or can i send sms to some cell via some python library? Waiting for advice. Thanks! Gerardo

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Re: list index()
by MRAB Aug. 30, 2007

Aug. 30, 2007

On Aug 30, 7:00 pm, Steve Holden <st...(a)holdenweb.com> wrote: > zzbba...(a)aol.com wrote: > >> How could it not be an exception, in the plain English sense of the > >> word? Most certainly you're asking for the index because you want to do > >> something with the index. If the item is not found, you have no index, > >> so that's a special case that must be handled separately. There is no > >> logical difference between handling that special case in an except > >> clause versus handling it with an if-branch. > > > In my case of have done os.listdir() on two directories. I want to see > > what files are in directory A that are not in directory B. > > I have used exceptions in other languages and only do so on logic that > > should never happen. In this case it is known that some of the files > > will not be in both lists. I just want to know which ones. > > And, as is so often the case, once the *real* problem is stated a more > elegant solution become available - in this case, using sets. > > afiles = set(os.listdir(dira)) > bfiles = set(os.listdir(dirb)) > > for f in (afiles - bfiles): > print "Not common:", f > > You can also generate the files that are in one directory but ot the > other with > > (afiles | bfiles) - (afiles & bfiles) > ... which can be written more concisely as: afiles ^ bfiles :-)

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Re: list index()
by zzbbaadd＠aol.com Aug. 30, 2007

Aug. 30, 2007

> That wish will only come true if you maintain your own fork of Python 3. > has_key() will go away, period. It has been made obsolete by "in", which > is faster and more concise. Is there really some reason "key" IN dict can be implemented faster than dict.has_key("key")???

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