🌐 Mailman 3 December 2009 - Python-list - python.org

the need for 64 bits
by Mensanator Dec. 30, 2009

Dec. 30, 2009

I routinely use large numbers in my Collatz Conjecture work. Really large. As in a quarter million bits. You wouldn't think that the processor would make all that much difference. But using the number is a doddle. The real trick is getting there. There is a limitation that few encounter. In an exponential, the exponent is limited to 32 bits, else you get an "outrageous exponent" error. But I assume that was due to integer size, that if you have 64 bit integers, the limit of the exponent ought to also be 64 bits. With my new MacBook replacing my old Windows laptop, I can try this. Using this function (which grows really large, really quick)... def Type12MH(k,i): """Find ith, kth Generation Type [1,2] Mersenne Hailstone using the closed form equation Type12MH(k,i) k: generation i: member of generation returns Hailstone (a) """ ONE = gmpy.mpz(1) TWO = gmpy.mpz(2) SIX = gmpy.mpz(6) NIN = gmpy.mpz(9) if (k<1) or (i<1): return 0 i = gmpy.mpz(i) k = gmpy.mpz(k) # a = (i-1)*9**(k-1) + (9**(k-1) - 1)//2 + 1 # return 2**(6*a - 1) - 1 a = (i-ONE)*NIN**(k-ONE) + (NIN**(k-ONE) - ONE)//TWO + ONE return TWO**(SIX*a - ONE) - ONE i: 1 bits: 5 decimals: 2 i: 2 bits: 29 decimals: 9 i: 3 bits: 245 decimals: 74 i: 4 bits: 2,189 decimals: 659 i: 5 bits: 19,685 decimals: 5,926 i: 6 bits: 177,149 decimals: 53,328 i: 7 bits: 1,594,325 decimals: 479,940 i: 8 bits: 14,348,909 decimals: 4,319,453 i: 9 bits: 129,140,165 decimals: 38,875,064 i: 10 bits: 1,162,261,469 decimals: 349,875,565 … my Windows/32-bit machine can't get past generation 10 without getting "outrageous exponent". But with a 64-bit processor, that limitation no longer stops me. i: 11 bits: 10,460,353,205 decimals: 3,148,880,080 i: 12 bits: 94,143,178,829 decimals: 28,339,920,715 Wow! 94 billion bits! 28 billion decimal digits! Of course, once one wall falls, you get to go up against the next one. For generation 13, I get: gmp: overflow in mpz type Abort trap Hmm, not sure what "overflow" means in this context, but I suspect it ran out of memory, I probably should have gotten the MacBook Pro with 8 GB of ram. But then, maybe it wouldn't help. Regardless, my window of research has gotten slightly larger.

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Re: detect interactivity
by Steven D'Aprano Dec. 30, 2009

Dec. 30, 2009

On Wed, 30 Dec 2009 03:33:18 +0100, Roald de Vries wrote: > I'm using a database, and want to use python interactively to manipulate > it. On the other hand, I also want to be able to use it non- > interactively. In that case, it would be a waste of CPU to load the > function/class definitions meant for interactive use. Premature optimization is the root of all evil. The code for interactive use almost certainly won't be a significant drain on the computer's resources, unless you're using some sort of embedded device. And if it is, then the natural overhead of merely running Python at all is almost certainly even more of a drain -- Python is not a language designed for the efficiency of the CPU, but for the programmer instead. But even if we give you the benefit of the doubt, and assume that you've profiled your code and determined that, in this case, such optimization is needed, I see at least two problems with that approach. Problem #1: the benefit won't be as much as you might expect. If your approach is the following: # common code used both interactively and non-interactively def parrot(): pass def spanish_inquisition(): pass # interactive code only: if interactive(): # however you determine this def cheeseshop(): pass then the approach you are trying isn't doing what you think it does. Python still has to parse the definition of cheeseshop and compile it before running the module code, so the benefit of making it optional is minimal. You might think that the better approach is to move it into another module: if interactive(): # however you determine this from interactive_code import * but even this means that the benefit is relatively small, since the interactive_code module will be compiled to a .pyc file, and therefore most of the effort of parsing it, compiling it etc. will be skipped. And now you have to deal with the problem of circular imports. Problem #2: if you have code that only appears at certain times, how do you test it to be sure it works correctly? Since test code (unit tests, doc tests, etc.) generally are run non- interactively, your code will be missing all the interactive functions, which means you can't test them easily. Any automated test suite will skip half your code! -- Steven

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Re: Thanks for the help not given :)
by aahz＠pythoncraft.com Dec. 30, 2009

Dec. 30, 2009

In article <mailman.177.1262121555.28905.python-list(a)python.org>, J <dreadpiratejeff(a)gmail.com> wrote: > >So though I've only posted a small bit here and on python-win, I did >want to thank y'all for helping me when you have, and even when you >actually haven't! Get a teddybear, that helps, too. ;-) (I.e. try to explain your problem to a teddybear.) -- Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/ Weinberg's Second Law: If builders built buildings the way programmers wrote programs, then the first woodpecker that came along would destroy civilization.

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Re: I think I found a bug in Python 2.6.4 (in the inspect module)
by Irmen de Jong Dec. 30, 2009

Dec. 30, 2009

On 29-12-2009 23:22, inhahe wrote: > On Tue, Dec 29, 2009 at 5:11 PM, inhahe<inhahe(a)gmail.com> wrote: >> On Tue, Dec 29, 2009 at 5:10 PM, inhahe<inhahe(a)gmail.com> wrote: >>> >>> So i'm guessing that the attribute has been changed from func_code to >>> f_code but the inspect module wasn't updated to reflect that. >>> >> >> er i mean from f_code to func_code >> > > f_locals doesn't even seem to exist at all. [...] I think there are 2 different things : f_code : 'the code object being executed in this frame' func_code : 'The code object representing the compiled function' That is, one is valid in the context of execution stack frames, while the other is valid in the context of compiled byte code objects that are generated for functions and so on. inspect.getargvalues is used on frames, not on regular code objects. Maybe you were looking for inspect.getargspec? -irmen

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Re: detect interactivity
by Steven D'Aprano Dec. 30, 2009

Dec. 30, 2009

On Tue, 29 Dec 2009 16:09:58 +0100, Roald de Vries wrote: > Dear all, > > Is it possible for a Python script to detect whether it is running > interactively? It can be useful for e.g. defining functions that are > only useful in interactive mode. Ah, I should have looked more carefully at the docs... http://docs.python.org/library/sys.html#sys.ps1 sys.ps1 and sys.ps2 are documented as only existing if you are running interactively. -- Steven

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Re: detect interactivity
by Steven D'Aprano Dec. 30, 2009

Dec. 30, 2009

On Tue, 29 Dec 2009 16:09:58 +0100, Roald de Vries wrote: > Dear all, > > Is it possible for a Python script to detect whether it is running > interactively? It can be useful for e.g. defining functions that are > only useful in interactive mode. Check __name__. It's set to '__main__' when running as a (non- interactive) script, and to the name of the module when imported. [steve@sylar ~]$ cat interactive.py print __name__ [steve@sylar ~]$ python interactive.py __main__ [steve@sylar ~]$ python Python 2.5 (r25:51908, Nov 6 2007, 16:54:01) [GCC 4.1.2 20070925 (Red Hat 4.1.2-27)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> >>> import interactive interactive >>> The only complications are that it doesn't work well with the -i command line switch (it still reports that __name__ == '__main__'), and if you start an interactive session __name__ is also set to '__main__'. Sadly, sys.argv doesn't report the switches used, but in Python 2.6 and better you can look at sys.flags to see if the -i switch is being used. http://docs.python.org/library/sys.html#sys.flags -- Steven

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Re: Moving from PHP to Python. Is it Possible
by Aaron Watters Dec. 30, 2009

Dec. 30, 2009

Sancar wants to move from PHP to Python. The following a shameless plug for WHIFF: http://whiff.sourceforge.net -- I wrote it partially because I wanted PHP-like features using Python, but better ;). On Dec 11, 5:26 am, Sancar Saran <sancar.sa...(a)evodot.com> wrote: > Greetings. > ....After 3 days of crawling google, diving in python and cursing, now I can show > something on my linux/apache/mod_wsgi setup. It's too bad you didn't find the WHIFF quickstart first :). http://whiffdoc.appspot.com/docs/W0500.quickstart > And i'm struck on something.... > > My design depends on a Global Array. A huge array which store everything about > requested Web page for a final rendering. > In PHP accessing globals is easy. You may do direct access or use class > something like ZEND Registry.... > 1-) Can I create Global (read/write access anywhere from my code) Multi > dimensional, associative array (or hash) and store any kind of variable type. There are a number of ways to do things like this in WHIFF -- one way is to use the WSGI environment to store your "globals" as illustrated in the Mako tutorial: http://whiffdoc.appspot.com/docs/W1100_1075.MakoGrading > 2-) Is there any error trigger for mod_wsgi. When something go bad I god > Internal Server error. Looking for error log was't nice. Is there any way to > shows errors in the web page ? Configure your application to display tracebacks on errors. I need to explicitly add this to the documentation, but here is an example used by the WHIFF documentation app config: 59 whiffDocumentation = resolver.moduleRootApplication("/", docroot, 60 #exception_middleware=None, 61 environment=environment, 62 exception_middleware=displayTraceback.__middleware__, 63 on_not_found=None, # show traceback (could comment) 64 auto_reload=False, 65 ) lines 62 and 63 from http://aaron.oirt.rutgers.edu/cgi-bin/whiffRepo.cgi/file/4b2cea3d92fc/doc/s… > 3-) Any documents books sites about helping moving from php to python http://whiffdoc.appspot.com/ (doesn't explicitly mention PHP). > 4-) In php we had something like > ob_start(); // start Output buffering > require('hede.php'); // include phtml similar to psp. mixed language and html > (to avoiding string replacement (or marker based) html templates) > $var = ob_get_clean(); // get rendered output and use anywhere > can find a similar abilities in Python ? Of course: See the quoteHtml implementation, for example http://aaron.oirt.rutgers.edu/cgi-bin/whiffRepo.cgi/file/4b2cea3d92fc/whiff… > 5-) is there any Python documentation based on examples. When I give up about > to finding php's $_REQUEST or $_SERVER equivalents in python some demo code in > Twisted docs are much helpful than any other words. Me and my kind already > have problem with English language. Example code much more helpful than full > academic description. http://whiffdoc.appspot.com (again) there are lots and lots of examples. I hope you like it and have a happy new year! -- Aaron Watters === my resolution last year was not to make any resolutions this year.

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I think I found a bug in Python 2.6.4 (in the inspect module)
by inhahe Dec. 29, 2009

Dec. 29, 2009

Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import inspect >>> def a(b=1): pass ... >>> inspect.getargvalues(a) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "C:\Python26\lib\inspect.py", line 816, in getargvalues args, varargs, varkw = getargs(frame.f_code) AttributeError: 'function' object has no attribute 'f_code' >>> dir(a) ['__call__', '__class__', '__closure__', '__code__', '__defaults__', '__delattr_ _', '__dict__', '__doc__', '__format__', '__get__', '__getattribute__', '__globa ls__', '__hash__', '__init__', '__module__', '__name__', '__new__', '__reduce__' , '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subcla sshook__', 'func_closure', 'func_code', 'func_defaults', 'func_dict', 'func_doc' , 'func_globals', 'func_name'] >>> So i'm guessing that the attribute has been changed from func_code to f_code but the inspect module wasn't updated to reflect that.

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Re: Another Sets Problem
by Stefan Behnel Dec. 29, 2009

Dec. 29, 2009

> Victor Subervi wrote: >> I'm using python 2.4.3 which apparently requires that I import Set: >> from sets import Set ... unless you use "set" instead of "Set". >> I've done this. In another script I successfully manipulated MySQL >> sets by so doing. Here's the code snippet from the script where I was >> able to call the elements in a for loop: >> >> if isinstance(colValue[0], (str, int, float, long, complex, >> unicode, list, buffer, xrange, tuple)): This line leaves me baffled. I guess a positive list would be less ugly here, and some more generic code that handles data values regardless of their exact type would be even better. >> html = "<b>%s</b>: <select name='%s'>" % (col, col) Note that there are tons of helpful libraries out there for generating HTML with Python. While string concatenation works in general, it also makes it very hard to get the output right, and to keep the output correct when you change minor stuff in your code. Given that you seem to pull data from a database into a web page, you might want to take a look at Django, for example. Stefan

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Re: Thanks for the help not given :)
by Ben Finney Dec. 29, 2009

Dec. 29, 2009

J <dreadpiratejeff(a)gmail.com> writes: > And each time, I started writing a post, complete with code samples > and my thoughts... and in EVERY case, so far, I've found the answer on > my own ONLY after writing that post. > […] actually writing out a post helps me organize my thoughts, the > problem, and what I've done so far, and usually THAT is when the > solution actually hits me. Even when I don't send the post, just > having a target that forces me to actually organize and spell out what > the problem is helps immensely. A very common experience, and I'm glad you've found it so consistently helpful <URL:http://en.wikipedia.org/wiki/Rubber_duck_debugging>. Thanks for telling us how well it works! -- \ “Our products just aren't engineered for security.” —Brian | `\ Valentine, senior vice-president of Microsoft Windows | _o__) development | Ben Finney

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