Introduction to Python, July 13-15, 2010 (Chicago)
Introduction to Python Programming with David Beazley, author Python Essential Reference http://www.dabeaz.com/chicago/index.html July 13-15, 2010 Chicago, Illinois Just a quick note to say that there are still a few slots available for my upcoming Introduction to Python Programming course. This is an intense no-bull course for programmers, sysadmins, scientists, and engineers who want to solve practical problems and improve their Python programming skills. This course is strictly limited to 6 people and is being held in the heart of Chicago's distinctive Andersonville neighborhood. Come hack some Python code while enjoying the summer sights, sounds, and tastes of the city. You won't be disappointed. Cheers, Dave -- http://mail.python.org/mailman/listinfo/python-announce-list Support the Python Software Foundation: http://www.python.org/psf/donations/
]ANN] Selenium Python bindings dev-9231
Hello All, The latest version of Selenium Python bindings (dev-9231 on PyPI) includes the native Firefox driver. You can now can do: from selenium import get_driver, FIREFOX driver = get_driver(FIREFOX) driver.get(http://www.google.com;) ... To get the latest version, just run easy_install -U selenium. Happy testing, -- Miki -- http://mail.python.org/mailman/listinfo/python-announce-list Support the Python Software Foundation: http://www.python.org/psf/donations/
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
sturlamolden sturlamol...@yahoo.no wrote: Just a little reminder: Microsoft has withdrawn VS2008 in favor of VS2010. Nonsense. They have released VS2010, but they certainly have not withdrawn VS2008, and I have heard of no plans to do so. The express version is also unavailable for download. :(( Also nonsense. Get it from right here: http://www.microsoft.com/express/downloads/ Note the three tabs: VS2010, SQL Server R2, and VS2008. -- Tim Roberts, t...@probo.com Providenza Boekelheide, Inc. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7/6/10 11:21 PM, Tim Roberts wrote: sturlamolden sturlamol...@yahoo.no wrote: Just a little reminder: Microsoft has withdrawn VS2008 in favor of VS2010. Nonsense. They have released VS2010, but they certainly have not withdrawn VS2008, and I have heard of no plans to do so. Its not nonsense; Microsoft has historically made unavailable fairly quickly previous versions of the suite after a new release is out. There hasn't been any serious notification of this before it happens. The concern here is not at all without precedent. There has been some very real pain for Python extension authors/maintainers directly related to what compilers and SDK's Microsoft makes available: generally, Python is 'behind' the times of what's the latest version of VS and their SDK that is available. The express version is also unavailable for download. :(( Also nonsense. Get it from right here: http://www.microsoft.com/express/downloads/ Note the three tabs: VS2010, SQL Server R2, and VS2008. Again, not nonsense. That's available now. However, very real experience has made certain people *very* reasonably cautious about when now becomes the past in this situation: what is available now may change as soon as tomorrow or later with very little real notice. Yeah, you can get a MSDN subscription and get access to a lot. Lots of people can't afford that just to compile an extension they support. -- Stephen Hansen ... Also: Ixokai ... Mail: me+list/python (AT) ixokai (DOT) io ... Blog: http://meh.ixokai.io/ signature.asc Description: OpenPGP digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Python as a scripting language. Alternative to bash script?
John Nagle, 28.06.2010 19:57: Programs have argv and argc, plus environment variables, going in. So, going in, there are essentially subroutine parameters. But all that comes back is an exit code. They should have had something similar coming back, with arguments to exit() returning the results. Then the many small intercommunicating programs concept would have worked much better. Except that you just broke the simplicity of the pipe mechanism. Stefan -- http://mail.python.org/mailman/listinfo/python-list
Python 3 - Is PIL/wxPython/PyWin32 supported?
Hi! I have an environment under Python 2.6 (WinXP). That is based on PIL, wxPython/PyWin32. In the project's pages I see official installer for only PyWin32. I don't know that PIL or wxPython supports Python 3 or not. May with some trick these packages are working. Does anybody know about it? Can I replace my Py2.6 without lost PIL/wxPython? Thanks for your help: dd -- http://mail.python.org/mailman/listinfo/python-list
Re: Plot problem.. ?? No sign at all
2010-07-06 19:18, Ritchy lelis skrev: On 6 jul, 17:29, Alan G Isaacalan.is...@gmail.com wrote: Unfortunately I cannot make sense of the code you posted. Provide a detailed description in words (or psuedocode) of what you are trying to accomplish. Be very careful and detailed is you want a useful response. Alan Isaac hummm... ok, i will try to make that detailed description. I can tell you why I do not understand from your posted code what you are trying to do. Firstly, I do not understand if you are trying to plot a surface, a set of curves, or a curve, or just a set of points? In your posted code, the plot command is part of the else clause, and my guess is that you never intend the else-clause to be executed at all. In your code snippet you loop over two arrays (Vi and Vref), compute a scalar value V0, and all plot-commands you issue are of the form plot(V0). This will probably draw a line of one point (for each value in Vi and Vref), which may not be what you want, and if it draws anything at all, then all points will be drawn at the same x-value, which is also probably not what you want. Secondly, how are the Vi and Vref related to your axes? I assume you want to plot all values you compute for V0, but as a function of what? When I use the plot command, I usually give it (at least) two arguments, where the first is the x-axis, and the second is the y-axis. After I have understood those things, the next question would be about the maths relating the Vi and Vref values to the V0 values, but I do not think I will understand those until after the above points are explained clearer. I definitely think your english is not a problem here. Johan -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Jul 6, 3:30 am, David Cournapeau courn...@gmail.com wrote: On Tue, Jul 6, 2010 at 4:30 AM, D'Arcy J.M. Cain da...@druid.net wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. This is exactly how I felt about my support for pyparsing, that I was trying continue to provide support for 2.3 users, up through 3.x users, with a single code base. (This would actually have been possible if I had been willing to introduce a performance penalty for Python 2 users, but performance is such a critical issue for parsing I couldn't justify it to myself.) This meant that I had to constrain my implementation, while trying to incorporate forward-looking support features (such as __bool__ and __dir__), which have no effect on older Python versions, but support additions in newer Pythons. I just couldn't get through on the python-dev list that I couldn't just upgrade my code to 2.6 and then use 2to3 to keep in step across the 2-3 chasm, as this would leave behind my faithful pre-2.6 users. Here are some of the methods I used: - No use of sets. Instead I defined a very simple set simulation using dict keys, which could be interchanged with set for later versions. - No generator expressions, only list comprehensions. - No use of decorators. BUT, pyparsing includes a decorator method, traceParseAction, which can be used by users with later Pythons as @traceParseAction in their own code. - No print statements. As pyparsing is intended to be an internal module, it does no I/O as part of its function - it only processes a given string, and returns a data structure. - Python 2-3 compatible exception syntax. This may have been my trickiest step. The change of syntax for except from except ExceptionType, ex: to: except ExceptionType as ex: is completely forward and backward incompatible. The workaround is to rewrite as: except ExceptionType: ex = sys.exc_info()[0] which works just fine in 2.x and 3.x. However, there is a slight performance penalty in doing this, and pyparsing uses exceptions as part of its grammar success/failure signalling and backtracking; I've used this technique everywhere I can get away with it, but there is one critical spot where I can't use it, so I have to keep 2 code bases with slight differences between them. - Implement __bool__, followed by __nonzero__ = __bool__. This will give you boolean support for your classes in 2.3-3.1. - Implement __dir__, which is unused by old Pythons, but supports customization of dir() output for your own classes. - Implement __len__, __contains__, __iter__ and __reversed__ for container classes. - No ternary expressions. Not too difficult really, there are several well-known workarounds for this, either by careful use of and's and or's, or using the bool-as-int to return the value from (falseValue,trueValue)[condition]. - Define a version-sensitive portion of your module, to define synonyms for constants that changed name between versions. Something like: _PY3K = sys.version_info[0] 2 if _PY3K: _MAX_INT = sys.maxsize basestring = str _str2dict = set alphas = string.ascii_lowercase + string.ascii_uppercase else: _MAX_INT = sys.maxint range = xrange _str2dict = lambda strg : dict( [(c,0) for c in strg] ) alphas = string.lowercase + string.uppercase The main body of my code uses range throughout (for example), and with this definition I get the iterator behavior of xrange regardless of Python version. In the end I still have 2 source files, one for Py2 and one for Py3, but there is only a small and manageable number of differences between them, and I expect at some point I will move forward to supporting Py3 as my primary target version. But personally I think this overall Python 2-3 migration process is moving along at a decent rate, and I should be able to make my switchover in another 12-18 months. But in the meantime, I am still able to support all versions of Python NOW, and I plan to continue doing so (albeit support for 2.x versions will eventually mean continue to offer a frozen feature set, with minimal bug-fixing if any). I realize that pyparsing is a simple-minded module in comparison to others: it is pure Python, so it has no issues with C extensions; it does no I/O, so print-as-statement vs. print-as-function is not an issue; and it imports few other modules, so the ones it does have not been dropped in Py3; and overall it is only a few thousand lines of code. But I just offer this post as a concrete data point in this discussion. -- Paul --
Re: The real problem with Python 3 - no business case for conversion
Paul McGuire pt...@austin.rr.com writes: is completely forward and backward incompatible. The workaround is to rewrite as: except ExceptionType: ex = sys.exc_info()[0] which works just fine in 2.x and 3.x. Are you sure? I wonder if there might be some race condition that could make it fail. I didn't even know about (or forgot) this change. Yucch. -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion
On 07/07/2010 10:58 AM, Paul Rubin wrote: Paul McGuire pt...@austin.rr.com writes: is completely forward and backward incompatible. The workaround is to rewrite as: except ExceptionType: ex = sys.exc_info()[0] which works just fine in 2.x and 3.x. Are you sure? I wonder if there might be some race condition that could make it fail. Luckily, no: (lib. docs on exc_info()) This function returns a tuple of three values that give information about the exception that is currently being handled. The information returned is specific both to the current thread and to the current stack frame. I didn't even know about (or forgot) this change. Yucch. -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Tue, Jul 6, 2010 at 1:37 AM, Terry Reedy tjre...@udel.edu wrote: On 7/5/2010 9:00 PM, Philip Semanchuk wrote: On Jul 5, 2010, at 6:41 PM, Chris Rebert wrote: On Mon, Jul 5, 2010 at 3:38 PM, Philip Semanchuk I ported two pure C extensions from 2 to 3 and was even able to keep a single C codebase. I'd be willing to contribute my experiences to a document somewhere. (Is there a Wiki?) Indeed there is: http://wiki.python.org/moin/ Thanks. I don't want to appear ungrateful, but I was hoping for something specific to the 2-to-3 conversion. I guess someone has to start somewhere... There is an existing 2to3 and other pages for Python code conversion. I do not know of any for CAPI conversion. The need for such has been acknowledged among the devs but if there is nothing yet, we need someone with specialized experience and a bit of time to make a first draft. If you start one, give it an easy to remember name C2to3? 2to3Capi? You choose. And link to it from the 2to3 page In his post on this thread, Martin Loewis volunteered to list what he knows from psycopg2 if someone else will edit. I'm not sure why I don't have this post, but I'm happy to help edit etc if Martin wants to put together a rough draft. Geremy Condra -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On Jul 6, 4:50 pm, sturlamolden sturlamol...@yahoo.no wrote: Just a little reminder: Microsoft has withdrawn VS2008 in favor of VS2010. The express version is also unavailable for download. :(( We can still get a VC++ 2008 compiler required to build extensions for the official Python 2.6 and 2.7 binary installers here (Windows 7 SDK for .NET 3.5 SP1): http://www.microsoft.com/downloads/details.aspx?familyid=71DEB800-C59... Download today, before it goes away! Microsoft has now published a download for Windows 7 SDK for .NET 4. It has the VC++ 2010 compiler. It can be a matter of days before the VC ++ 2008 compiler is totally unavailable. I presume this problem would go away if future versions of Python itself were compiled on Windows with something like MinGW gcc. Also, this would solve the pain of Python developers attempting to redistribute py2exe versions of their programs (i.e. they have to own a Visual Studio license to legally be able to redistribute the required C runtime) I don't understand enough to know why Visual Studio was chosen instead of MinGW. Can anyone shed any light on that decision? Many thanks Jonathan Hartley -- http://mail.python.org/mailman/listinfo/python-list
Problem With the PyRtf Footers
Hi all, Am using the pyrtf for the generating the rtf documents from the html.Am able to generate the documents the problem is with the footer.Its coming only for the first page for the rest of the pages it is coming empty.Am using the section.FirstFooter for the first page footer and section.Footer for the subsequent pages.I am not able to figure out what is exactly the problem.If any body knows please help me. Thanks in Advance ! Srinivas HN ph-9986229891 -- http://mail.python.org/mailman/listinfo/python-list
Python -- floating point arithmetic
Dear Python-User, today i create some slides about floating point arithmetic. I used an example from http://docs.python.org/tutorial/floatingpoint.html so i start the python shell on my linux machine: d...@maxwell $ python Python 2.6.5 (release26-maint, May 25 2010, 12:37:06) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. So i create an example program: sum = 0.0 n = 10 d = 1.0 / n print %.60f % ( d ) for i in range(n): print %.60f % ( sum ) sum += d print sum print %.60f % ( sum ) RESULTs -- 0.1555111512312578270211815834045410156250 0. 0.1555111512312578270211815834045410156250 0.20001110223024625156540423631668090820312500 0.3000444089209850062616169452667236328125 0.40002220446049250313080847263336181640625000 0.5000 0.59997779553950749686919152736663818359375000 0.6999555910790149937383830547332763671875 0.79993338661852249060757458209991455078125000 0.8999111821580299874767661094665527343750 1.0 0.99988897769753748434595763683319091796875000 and the jump from 0.50*** to 0.5999* looks wrong for me ... do i a mistake or is there something wrong in the representation of the floating points in python? my next question, why could i run print %.66f % ( sum ) but not print %.67f % ( sum ) can anybody tell me how python internal represent a float number?? Best and many thanks in advanced, David -- http://mail.python.org/mailman/listinfo/python-list
Python -- floating point arithmetic
-BEGIN PGP SIGNED MESSAGE- Hash: SHA384 Dear Python-User, today i create some slides about floating point arithmetic. I used an example from http://docs.python.org/tutorial/floatingpoint.html so i start the python shell on my linux machine: d...@maxwell $ python Python 2.6.5 (release26-maint, May 25 2010, 12:37:06) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. So i create an example program: sum = 0.0 n = 10 d = 1.0 / n print %.60f % ( d ) for i in range(n): print %.60f % ( sum ) sum += d print sum print %.60f % ( sum ) - RESULTs -- 0.1555111512312578270211815834045410156250 0. 0.1555111512312578270211815834045410156250 0.20001110223024625156540423631668090820312500 0.3000444089209850062616169452667236328125 0.40002220446049250313080847263336181640625000 0.5000 0.59997779553950749686919152736663818359375000 0.6999555910790149937383830547332763671875 0.79993338661852249060757458209991455078125000 0.8999111821580299874767661094665527343750 1.0 0.99988897769753748434595763683319091796875000 and the jump from 0.50*** to 0.5999* looks wrong for me ... do i a mistake or is there something wrong in the representation of the floating points in python? my next question, why could i run print %.66f % ( sum ) but not print %.67f % ( sum ) can anybody tell me how python internal represent a float number?? Best and many thanks in advanced, David -BEGIN PGP SIGNATURE- Version: GnuPG v2.0.15 (GNU/Linux) iQIcBAEBCQAGBQJMNGpsAAoJEJ82b5xvAlAYYMYP/RTaRcB2NCawBQ25V463+pkO /YtTqsamrFqENrljqpsPrwOOqR02TQrOvZrV72snDPkkcN36tZHKwbmcnOS0tOAc kjX0/oNQOvvEMyJUuHJt9kdNjxMEvUUlENEZHLtpxbypIAo3Waf0FBxKo9F4fJJS PaDIuDgXiLOiaTTUCwa5kKowzjUe8BJOczpUulvGiIvbUac4cxwkPiGvv6L4wzmI /4x1mG5FSibEzcI2zFRsQNHfTqxuKC3a49DuSPtXZo4YWdqVeSXLntQk70uTa78K q4cBVEIDqETQyG0mcRABJpcTMPsnGgbgJD74uhDSTARuyHh405XbjKlic7pe1M12 AhuN71QjpGFl80OOXxCja4OKJCAhPEkfhNsJjrlFnSXAoFWg5YvhDbSVkjW6ftt0 tzyGZEoBpRSjGSIeAojYaqt1Xdxwldz2qFjRLX03io3Fgr8PKRbcLRgg1FXaMFPc gYaY0UEh4dEjt/5afp3ET0LkOhZVMbbi2oSkkFQpRMAzik63zSJRwRxiQXWunlSi HhKqL4sAICf6MODzquuNzJO9wH8Fkpwi+JPEAwnQm/S6Ty00dN22GezG4TWGfepH AhKOIEtRIcMgI7kyBfUdOQe6sifKGGuTEeXK12Td9znZN+wKfqG+Ch1mq4Rwy6P7 p2xwF7ZUWNgRU+5Y/bLG =aS+I -END PGP SIGNATURE- -- http://mail.python.org/mailman/listinfo/python-list
Re: Recommend a MySQLdb Forum
On Jul 6, 2010, at 3:16 PM, Tim Johnson wrote: Greetings: I would appreciate it if some could recommend a MySQLdb forum. The one associated the sourceforge project seems like a good bet. 1) go here: http://sourceforge.net/projects/mysql-python/ 2) click support -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
On Jul 7, 1:05 pm, david mainzer d...@tu-clausthal.de wrote: Dear Python-User, today i create some slides about floating point arithmetic. I used an example from http://docs.python.org/tutorial/floatingpoint.html so i start the python shell on my linux machine: d...@maxwell $ python Python 2.6.5 (release26-maint, May 25 2010, 12:37:06) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. So you've identified one source of error here, namely that 0.1 isn't exactly representable (and you're correct that the value stored internally is actually a little greater than 0.1). But you're forgetting about the other source of error in your example: when you do 'sum += 0.1', the result typically isn't exactly representable, so there's another rounding step going on. That rounding step might produce a number that's smaller than the actual exact sum, and if enough of your 'sum += 0.1' results are rounded down instead of up, that would easily explain why the total is still less than 1.0. So i create an example program: sum = 0.0 n = 10 d = 1.0 / n print %.60f % ( d ) for i in range(n): print %.60f % ( sum ) sum += d print sum print %.60f % ( sum ) RESULTs -- 0.1555111512312578270211815834045410156250 0. 0.1555111512312578270211815834045410156250 0.20001110223024625156540423631668090820312500 0.3000444089209850062616169452667236328125 0.40002220446049250313080847263336181640625000 0.5000 0.59997779553950749686919152736663818359375000 0.6999555910790149937383830547332763671875 0.79993338661852249060757458209991455078125000 0.8999111821580299874767661094665527343750 1.0 0.99988897769753748434595763683319091796875000 and the jump from 0.50*** to 0.5999* looks wrong for me ... do i a mistake or is there something wrong in the representation of the floating points in python? Look at this more closely: you're adding 0.5000 to 0.155511151231257827021181583404541015625 The *exact* result is, of course 0.655511151231257827021181583404541015625 However, that's not a number that can be exactly represented as a C double (which is how Python stores floats internally). This value falls between the two (consecutive) representable values: 0.59997779553950749686919152736663818359375 and 0.600088817841970012523233890533447265625 But of these two, the first is closer to the exact value than the second, so that's the result that you get. You can convince yourself of these results by using the fractions module to do exact arithmetic: from fractions import Fraction tenth = Fraction.from_float(0.1) half = Fraction.from_float(0.5) point_six = Fraction.from_float(0.6) # 0.5999 point_six_plus = Fraction.from_float(0.6 + 2**-53) # next float up, 0.600 sum = tenth + half # exact value of the sum point_six sum point_six_plus# lies between point_six and point_six_plus True sum - point_six point_six_plus - sum # but it's closer to point_six True my next question, why could i run print %.66f % ( sum ) but not print %.67f % ( sum ) That's a historical artefact resulting from use of a fixed-length buffer somewhere deep in Python's internals. This restriction is removed in Python 2.7 and Python 3.x. can anybody tell me how python internal represent a float number?? In CPython, it's stored as a C double, which typically means in IEEE 754 binary64 format. (Of course, since it's a Python object, it's not just storing the C double itself; it also has fields for the object type and the reference count, so a Python float typically takes 16 bytes of memory on a 32-bit machine, and 24 bytes on a 64-bit machine.) -- Mark -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
On 07/07/2010 02:05 PM, david mainzer wrote: today i create some slides about floating point arithmetic. I used an example from http://docs.python.org/tutorial/floatingpoint.html so i start the python shell on my linux machine: d...@maxwell $ python Python 2.6.5 (release26-maint, May 25 2010, 12:37:06) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. The simple fact of the matter is: floating point arithmetic isn't accurate. This has nothing to do with Python, it's the fault of your processor's floating point handling. It's good enough in most cases, but you should never rely on a floating-point number to have exactly a certain value. It won't work. To generalize your example a bit: def test_floating_product(a, b): ... sum = 0 ... for _ in range(int(b)): ... sum += a ... return sum, a * int(b), sum == a * b ... test_floating_product(0.1, 1) (0.1, 0.1, True) test_floating_product(0.1, 10) (0., 1.0, False) test_floating_product(0.2, 4) (0.8, 0.8, True) test_floating_product(0.2, 5) (1.0, 1.0, True) test_floating_product(0.2, 6) (1.2, 1.2002, False) RESULTs -- 0.1555111512312578270211815834045410156250 0. 0.1555111512312578270211815834045410156250 0.20001110223024625156540423631668090820312500 0.3000444089209850062616169452667236328125 0.40002220446049250313080847263336181640625000 0.5000 0.59997779553950749686919152736663818359375000 0.6999555910790149937383830547332763671875 0.79993338661852249060757458209991455078125000 0.8999111821580299874767661094665527343750 1.0 0.99988897769753748434595763683319091796875000 and the jump from 0.50*** to 0.5999* looks wrong for me ... do i a mistake or is there something wrong in the representation of the floating points in python? the difference is almost exactly 0.1, so that looks okay my next question, why could i run print %.66f % ( sum ) but not print %.67f % ( sum ) I can run either... with Python 3.1. Using 2.6, I get a nice error message: %.129f % 0.1 Traceback (most recent call last): File stdin, line 1, in module OverflowError: formatted float is too long (precision too large?) There just isn't anything like 67 decimals of information available. Having that information wouldn't help you a bit. basically, floating point number are stored in the format N * (2 ** E) And use a lot of guesswork. as E gets larger, the precision decreases. Rounding errors occur at the last few decimals, in either direction, depending on the numbers. can anybody tell me how python internal represent a float number?? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
can anybody tell me how python internal represent a float number?? It's an IEEE 754 double precision float on all hardware platforms that support IEEE 754 semantics. Python follows the C99 standards for double and complex numbers. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: C interpreter in Lisp/scheme/python
Tim Rentsch t...@alumni.caltech.edu wrote: nanothermite911fbibustards nanothermite911fbibusta...@gmail.com How to make Lisp go faster than C Didier Verna Asking whether Lisp is faster than C is like asking why it's colder in the mountains than it is in the summer. YM warmer. HTH; HAND. Richard -- http://mail.python.org/mailman/listinfo/python-list
Re: Python 3 - Is PIL/wxPython/PyWin32 supported?
I don't know that PIL or wxPython supports Python 3 or not. May with some trick these packages are working. Does anybody know about it? Can I replace my Py2.6 without lost PIL/wxPython? PIL currently does not support python 3 but release 1.1.7 will in the future. Don't ask me when, I don't know. I have no idea about the rest. Cheers, Daniel -- Psss, psss, put it down! - http://www.cafepress.com/putitdown -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
On Jul 7, 2010, at 9:08 AM, Thomas Jollans wrote: On 07/07/2010 02:05 PM, david mainzer wrote: today i create some slides about floating point arithmetic. I used an example from http://docs.python.org/tutorial/floatingpoint.html so i start the python shell on my linux machine: d...@maxwell $ python Python 2.6.5 (release26-maint, May 25 2010, 12:37:06) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. The simple fact of the matter is: floating point arithmetic isn't accurate. This has nothing to do with Python, it's the fault of your processor's floating point handling. It's good enough in most cases, but you should never rely on a floating-point number to have exactly a certain value. It won't work. Yes, this might be a good time to review the dense but interesting document, What Every Computer Scientist Should Know About Floating- Point Arithmetic: http://docs.sun.com/source/806-3568/ncg_goldberg.html Cheers Philip -- http://mail.python.org/mailman/listinfo/python-list
Re: Why Python forbids multiple instances of one module?
Why Python forbids multiple instances of one module? If only Python allows multiple instances of one module, module will be enough to replace class in most cases. After all, it is much easier to write a module than a class, at least we do not have to write self everywhere. If you really want to do that, it should be possible by deleting the entry from sys.modules and re-importing it. You save yourself having to explicitly write self everywhere, but instead you have to declare all your instance variables as globals in each method that uses them, which isn't much less of a chore. You also lose inheritance, properties (and descriptors in general), magic method support, metaclasses, and pretty much all the other nice features that new-style classes have to offer. Wow, it works! Thanks a lot for the good idea. It is cool to write, test, debug and maintain POP codes, while realizing the OOP power. I think inheritance might be simulated with: from parentModule import * I really expect for the day when operator overloading and new-style class features find their way into module. Thans again.-- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
david mainzer wrote: sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. So i create an example program: sum = 0.0 n = 10 d = 1.0 / n print %.60f % ( d ) for i in range(n): print %.60f % ( sum ) sum += d print sum print %.60f % ( sum ) - RESULTs -- 0.1555111512312578270211815834045410156250 0. 0.1555111512312578270211815834045410156250 0.20001110223024625156540423631668090820312500 0.3000444089209850062616169452667236328125 0.40002220446049250313080847263336181640625000 0.5000 0.59997779553950749686919152736663818359375000 0.6999555910790149937383830547332763671875 0.79993338661852249060757458209991455078125000 0.8999111821580299874767661094665527343750 1.0 0.99988897769753748434595763683319091796875000 and the jump from 0.50*** to 0.5999* looks wrong for me ... do i a mistake or is there something wrong in the representation of the floating points in python? I think the main problem is, as sum gets bigger, the less significant bits of the 0.1 representation fall off the end (enough to make it effectively just under 0.1 you're adding instead of just over). can anybody tell me how python internal represent a float number?? Try google ieee floating point. The problems aren't specific to Python. -- Bartc -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
david mainzer wrote: sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. So i create an example program: sum = 0.0 n = 10 d = 1.0 / n print %.60f % ( d ) for i in range(n): print %.60f % ( sum ) sum += d print sum print %.60f % ( sum ) - RESULTs -- 0.1555111512312578270211815834045410156250 0. 0.1555111512312578270211815834045410156250 0.20001110223024625156540423631668090820312500 0.3000444089209850062616169452667236328125 0.40002220446049250313080847263336181640625000 0.5000 0.59997779553950749686919152736663818359375000 0.6999555910790149937383830547332763671875 0.79993338661852249060757458209991455078125000 0.8999111821580299874767661094665527343750 1.0 0.99988897769753748434595763683319091796875000 and the jump from 0.50*** to 0.5999* looks wrong for me ... do i a mistake or is there something wrong in the representation of the floating points in python? I think the main problem is, as sum gets bigger, the less significant bits of the 0.1 representation fall off the end (enough to make it effectively just under 0.1 you're adding instead of just over). can anybody tell me how python internal represent a float number?? Try google ieee floating point. The problems aren't specific to Python. -- Bartc -- http://mail.python.org/mailman/listinfo/python-list
Re: C interpreter in Lisp/scheme/python
On Jun 14, 1:07 am, bolega gnuist...@gmail.com wrote: I am trying to compare LISP/Scheme/Python for their expressiveness. For this, I propose a vanilla C interpreter. I have seen a book which writes C interpreter in C. The criteria would be the small size and high readability of the code. Are there already answers anywhere ? How would a gury approach such a project ? Bolega This look like a huge project for an evaluation of expressiveness which result is obvious. Lisp (including Scheme) is more expressive than Python, for many definitions of expressiveness (see for instance http://www.ccs.neu.edu/scheme/pubs/scp91-felleisen.ps.gz if you like academic papers). However, who cares? What matters in everyday life are other things, like the availability of libraries, tools, easy of maintenance, etc. In your proposed project the choice of the parsing library would matter a lot. Writing languages is a domain where Lisp is traditionally strong, so you may find good libraries to help you with the task. My guess is that it would take more or less the same amount of effort both in Python and in Lisp. The place where Lisp has an advantage is writing an *embedded* language: then thanks to macros you could write a *compiled* sublanguage. Doing the same in Python is essentially impossible. Michele Simionato -- http://mail.python.org/mailman/listinfo/python-list
Error message repetition
Hello! I have such problem that: - My console shows maximally x last lines, then truncates - Error message takes 2 line - In case of very big stack trace, there will be 2*x error lines - In such case I do not see any debug output In this case, it's about recursion: File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) and so on... I think it should be instead: File b2.py, line 124, in seek_solution [*repeated x times*] solution = self.seek_solution(weight + U.gravity, len(test), test) Getting big strack trace is most probable with functions calling themselves - thus, long stack traces usually contain such repetitions. As those functions might not call themselves directly, one cycle of recursion might become four lines long, in such case: Stack item 1: File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) Stack item 2: File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) Stack item repetitions: [#1, #2] * x This could simply enumerate stack items and then create formulas of repetitions, like: [[#1, #2] * 15, #3 * 15] * 3 If it shows each message written-out at least one and max two or three times, but over that gives it an id and shows patterns of those instead, it will be a lot better. I have, sometimes, gone through some four pages of Java stack traces etc., but I think that having such long array of errors does not make it more readable or simple - if you can see everything in one page, then it's good enough for pondering. And scrolling up and looking at output would be a nice feature ;) Especially now, as I am going to raise recursion limit - this program would be perfectly possible without relying on built-in loop constructions so much, but I did it yesterday in such manner and it simply raised into unmanageable complexity. Thus, now I am trying to encapsulate it's logic into pieces, which maximize the use of Pythons overloads and function-based iterators etc., but this makes error messages that long when I do something wrong - and I can't even check if that was really some mistake in code or just the recursion actually needs to be deeper than I hoped. Tambet -- http://mail.python.org/mailman/listinfo/python-list
tarfile and progress information
Hi, I am packing large files with tarfile. Is there any way I can get progress information while packing? Thanks! Nathan -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On 7/2/10 3:07 PM, John Nagle wrote: That's the real issue, not parentheses on the print statement. Where's the business case for moving to Python 3? It's not faster. It doesn't do anything you can't do in Python 2.6. There's no killer app for it. End of life for Python 2.x is many years away; most server Linux distros aren't even shipping with 2.6 yet. How can a business justify spending money on conversion to Python 3? That's decision for each business to make. My guess is that many businesses won't upgrade for some time, until the major libraries/modules support Python 3. I don't plan to move to Python 3 for at least a couple of years. Python 3 is a nice cleanup of some legacy syntax issues. But that's just not enough. Perl 6 is a nice cleanup of Perl 5, and look how that went. Ten years on, it's not even mainstream, let alone dominant. The Perl analogy isn't really useful here. Perl 6 is somewhere between the HURD and Duke Nukem Forever in terms of being viable. Even the Perl website says, If you are looking for production ready code please use Perl 5. That's one reason why Perl 5 development has recently undergone a resurgence. Python 3, by contrast, is production-ready in itself; libraries are gradually moving to support it, and Python 2 has a definite end-of-life release in 2.7, with an extended maintenance period for 2.7. The Python developers are providing a much stronger and clearer path forward for Python 3. The transition period may last five years, but the path is clear. As a Mac developer, I'm sympathetic to your frustration. A few years ago Apple deprecated one of its major API's (Carbon), on which my own development depended, and there was a lot of uncertainty about major libraries that use Carbon being updated. This is normal in any transition period. Eventually, the major libraries I depend on were updated by their developers (i.e. ported to the Cocoa API), I was able to migrate my own applications to the updated libraries, and life went on. I think the same thing will happen with Python. It's useful to note the libraries that are not yet ported to support Python 3, and to share best practices for moving forward. Past a certain point, however, I don't see much point in attacking the existence of Python 3 or questioning the need to move toward Python 3. It's here, it's the way forward, and that's not going to change. Might as well accept it. --Kevin -- Kevin Walzer Code by Kevin http://www.codebykevin.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Error message repetition
On 07/07/2010 05:10 PM, Tambet wrote: Hello! I have such problem that: * My console shows maximally x last lines, then truncates * Error message takes 2 line * In case of very big stack trace, there will be 2*x error lines * In such case I do not see any debug output In this case, it's about recursion: File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) and so on... Depending on how far this goes up, you might just be able to change the backlog your terminal emulator saves? that would allow you to scroll up. If you can't do that, you should get a proper console. Anyway, if you want to customise the traceback output, you can! simply replace sys.excepthook with your own version. http://docs.python.org/dev/py3k/library/sys.html#sys.excepthook I think it should be instead: File b2.py, line 124, in seek_solution [*repeated x times*] solution = self.seek_solution(weight + U.gravity, len(test), test) Getting big strack trace is most probable with functions calling themselves - thus, long stack traces usually contain such repetitions. As those functions might not call themselves directly, one cycle of recursion might become four lines long, in such case: Stack item 1: File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) Stack item 2: File b2.py, line 124, in seek_solution solution = self.seek_solution(weight + U.gravity, len(test), test) Stack item repetitions: [#1, #2] * x This could simply enumerate stack items and then create formulas of repetitions, like: [[#1, #2] * 15, #3 * 15] * 3 If it shows each message written-out at least one and max two or three times, but over that gives it an id and shows patterns of those instead, it will be a lot better. I have, sometimes, gone through some four pages of Java stack traces etc., but I think that having such long array of errors does not make it more readable or simple - if you can see everything in one page, then it's good enough for pondering. And scrolling up and looking at output would be a nice feature ;) Especially now, as I am going to raise recursion limit - this program would be perfectly possible without relying on built-in loop constructions so much, but I did it yesterday in such manner and it simply raised into unmanageable complexity. Thus, now I am trying to encapsulate it's logic into pieces, which maximize the use of Pythons overloads and function-based iterators etc., but this makes error messages that long when I do something wrong - and I can't even check if that was really some mistake in code or just the recursion actually needs to be deeper than I hoped. Tambet -- http://mail.python.org/mailman/listinfo/python-list
Re: Python as a scripting language. Alternative to bash script?
On 07/06/2010 09:34 PM, Chris Rebert wrote: On Tue, Jul 6, 2010 at 6:40 AM, Michael Torrie torr...@gmail.com wrote: While it's possible to set up pipes and spawn programs in parallel to operate on the pipes, in practice it's simpler to tell subprocess.Popen to use a shell and then just rely on Bash's very nice syntax for setting up the pipeline. Until there's a Python variable involved that is, unless you want to overlook all the edge cases or do the escaping all by yourself (and then pray you did it right). Very good point. This is a problem that the pipes module suffers from as well. Although we learned in the other thread on escaping SQL statements that escaping is faster, easier and just as safe as other parameterization mechanisms. Uh huh. Back on target, a library similar to pipes that was safe (pipes is not) and had a pythonic syntax would be cool. pipes module works alright, syntax wise, but it's not a clean syntax. -- http://mail.python.org/mailman/listinfo/python-list
Re: Error message repetition
Depending on how far this goes up, you might just be able to change the backlog your terminal emulator saves? that would allow you to scroll up. If you can't do that, you should get a proper console. I use bash, which allows to do that. This was rather a case example - actually this output gets pretty annoying anyway and should contain only most important information at any given moment. Scrollbar getting too small is another example of the same case ...the case that if something outputs 2000 lines of repetition, it's not very much of use. This could be that someone does not understand the cryptic output, but I think that anyone having that long traceback is probably intelligent enough to google for Python traceback what those cryptic things mean ;) I think that this functionality should be triggered only by traceback bigger than, say, 20 lines or so. Also, this is not the point, where processor usage costs anything. Anyway, if you want to customise the traceback output, you can! simply replace sys.excepthook with your own version. http://docs.python.org/dev/py3k/library/sys.html#sys.excepthook Ok, I should have thought of that - anyway, such thing should be standard functionality. I personally love nonverbose output - if it can't say it in 1 A4, it should just tell me that it could if I asked. I mean, normally I like to have one sight over the traceback and another over program itself. Thanks for that hook ...I will use it in case I get four of five more similar errors today ;) -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
On Wed, 07 Jul 2010 15:08:07 +0200, Thomas Jollans wrote: you should never rely on a floating-point number to have exactly a certain value. Never is an overstatement. There are situations where you can rely upon a floating-point number having exactly a certain value. First, floating-point values are exact. They may be an approximation to some other value, but they are still exact values, not some kind of indeterminate quantum state. Specifically, a floating-point value is a rational number whose denominator is a power of two. Second, if the result of performing a primitive arithmetic operation (addition, subtraction, multiplication, division, remainder) or the square-root function on the equivalent rational values is exactly representable as a floating-point number, then the result will be exactly that value. Third, if the result of performing a primitive arithmetic operation or the square-root function on the equivalent rational values *isn't* exactly representable as a floating-point number, then the floating-point result will be obtained by rounding the exact value according to the FPU's current rounding mode. All of this is entirely deterministic, and follows relatively simple rules. Even if the CPU has a built-in random number generator, it will *not* be used to generate the least-significant bits of a floating-point arithmetic result. The second and third cases above assume that floating-point arithmetic follows IEEE-754 (the second case is likely to be true even for systems which don't strictly adhere to IEEE-754). This is true for most modern architectures, provided that: 1. You aren't using Borland C, which forcibly optimises x/y to x*(1/y), so 12/3 isn't exactly equal to 4, as 1/3 isn't exactly representable. Real compilers won't use this sort of approximation unless specifically instructed (e.g. -funsafe-math-optimizations for gcc). 2. You aren't using one of the early Pentium chips. In spite of this, there are some gotchas. E.g. on x86, results are computed to 80-bit (long double) precision internally. These will be truncated to 64 bits if stored in memory. Whether the truncation occurs is largely up to the compiler, although it can be forced with -ffloat-store with gcc. More complex functions (trigonometric, etc) are only accurate to within a given relative error (e.g. +/- the value of the least significant bit), as it isn't always possible to determine the correct value for the least significant bit for a given rounding mode (and even if it is theoretically possible, there is no limit to the number of bits of precision which would be required). -- http://mail.python.org/mailman/listinfo/python-list
Re: C interpreter in Lisp/scheme/python
On Jun 13, 4:07 pm, bolega gnuist...@gmail.com wrote: I am trying to compare LISP/Scheme/Python for their expressiveness. For this, I propose a vanilla C interpreter. I have seen a book which writes C interpreter in C. The criteria would be the small size and high readability of the code. Are there already answers anywhere ? How would a gury approach such a project ? Bolega You should probably narrow down your project to one. For example, write a LISt Processor Meta Circular Evaluator in C. You can take Paul Graham's rendition as a start and forget about garbage collection. Start with getchar()/putchar() for I/O. Although C comes with a regex library, you probably do not need a regex or parser at all for this. This is the beauty of LISP which is why McCarthy was able to bypass the several man years of effort involved in FORmula TRANslator. Even as a young boy like L. Peter Deutsch was able to write it in assembly for one of the PDP's. You will have go implement an associative array or a symbol-value table probably as a stack or linked list. You will have to decide how you implement the trees, as cons cells or some other method. Dynamic scoping is easy to implement and that is what elisp has. I am not aware of any book that provides implementation of LISP in C and explains it at the same time. This is the extent of help I can provide, someone else can probably help you more. Anyone know what the first initial of L. Peter Deutsch stand for ? Rivka -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
In article 5325a$4c349b5b$4275d90a$27...@fuse.net, Kevin Walzer k...@codebykevin.com wrote: That's decision for each business to make. My guess is that many businesses won't upgrade for some time, until the major libraries/modules support Python 3. I don't plan to move to Python 3 for at least a couple of years. It takes a long time for big businesses to upgrade. It's not like me or you. I just download the latest and greatest, run the installer, and I'm good to go. A big company has to install it in a test lab, certify it, get approval from IT, log a change request, etc. You need to get approval from your manager, your director, your VP, and so on up the management chain until you finally reach somebody who has no clue what's going on and either sits on the request or denies it out of ignorance. Or, more likely, you just hit some middle-management layer where the guy doesn't have the authority to approve it himself, and isn't willing to expend the political capital it would take to get approval from the next layer up. Somebody might decide they don't want to disturb any existing production systems (not a bad idea, really), so you need to order new hardware for it. Even if you can get capital approval for that, it mushrooms into finding rack space, and the UPS is already oversubscribed, and so is the cooling, and there's no available network ports, and so on. Suddenly, downloading some free software has become a 5-figure project. Big businesses have lots of ways to ensure that no progress is ever made. If you think any of the above is made up, you've never worked for a big company. -- http://mail.python.org/mailman/listinfo/python-list
Re: C interpreter in Lisp/scheme/python
On 20 June, 03:48, Tim Rentsch t...@alumni.caltech.edu wrote: nanothermite911fbibustards nanothermite911fbibusta...@gmail.com writes: Asking whether Lisp is faster than C is like asking why it's colder in the mountains than it is in the summer. original Karl Valentin would be colder outside than nighttime but yours is in his sense. Wolfgang -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
Nobody wrote: On Wed, 07 Jul 2010 15:08:07 +0200, Thomas Jollans wrote: you should never rely on a floating-point number to have exactly a certain value. Never is an overstatement. There are situations where you can rely upon a floating-point number having exactly a certain value. It's not much of an overstatement. How many areas are there where you need the number 0.155511151231257827021181583404541015625000? If I'm looking for 0.1, I will *never* (except by accident ;) say if var == 0.1: it'll either be = or =. By contrast, if I'm dealing with integers I can say if var == 4 because I *know* that there are values that var can hold that are *exactly* 4. Not 3.9817263 or 4.19726. ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: Python 3 - Is PIL/wxPython/PyWin32 supported?
2010/7/7 durumdara durumd...@gmail.com: Hi! I have an environment under Python 2.6 (WinXP). That is based on PIL, wxPython/PyWin32. In the project's pages I see official installer for only PyWin32. I don't know that PIL or wxPython supports Python 3 or not. May with some trick these packages are working. Does anybody know about it? Can I replace my Py2.6 without lost PIL/wxPython? Thanks for your help: dd -- http://mail.python.org/mailman/listinfo/python-list No, as of now you just can't. Now that 2.7 is out and is officially declared as the last 2.x release it's likely that there will be a lot more traction in porting such big names to Python 3. --- Giampaolo http://code.google.com/p/pyftpdlib/ http://code.google.com/p/psutil/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
On Jul 7, 5:55 am, Mark Dickinson dicki...@gmail.com wrote: On Jul 7, 1:05 pm, david mainzer d...@tu-clausthal.de wrote: Dear Python-User, today i create some slides about floating point arithmetic. I used an example from http://docs.python.org/tutorial/floatingpoint.html so i start the python shell on my linux machine: d...@maxwell $ python Python 2.6.5 (release26-maint, May 25 2010, 12:37:06) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. sum = 0.0 for i in range(10): ... sum += 0.1 ... sum 0.99989 But thats looks a little bit wrong for me ... i must be a number greater then 1.0 because 0.1 = 0.155511151231257827021181583404541015625000 in python ... if i print it. [Mark Dickinson] So you've identified one source of error here, namely that 0.1 isn't exactly representable (and you're correct that the value stored internally is actually a little greater than 0.1). But you're forgetting about the other source of error in your example: when you do 'sum += 0.1', the result typically isn't exactly representable, so there's another rounding step going on. That rounding step might produce a number that's smaller than the actual exact sum, and if enough of your 'sum += 0.1' results are rounded down instead of up, that would easily explain why the total is still less than 1.0. One key for understanding floating point mysteries is to look at the actual binary sums rather that their approximate representation as a decimal string. The hex() method can make it easier to visualize Mark's explanation: s = 0.0 for i in range(10): ... s += 0.1 ... print s.hex(), repr(s) 0x1.ap-4 0.10001 0x1.ap-3 0.20001 0x1.4p-2 0.30004 0x1.ap-2 0.40002 0x1.0p-1 0.5 0x1.3p-1 0.59998 0x1.6p-1 0.69996 0x1.9p-1 0.79993 0x1.cp-1 0.89991 0x1.fp-1 0.99989 Having used hex() to understand representation error (how the binary partial sums are displayed), you can use the Fractions module to gain a better understanding of rounding error introduced by each addition: s = 0.0 for i in range(10): exact = Fraction.from_float(s) + Fraction.from_float(0.1) s += 0.1 actual = Fraction.from_float(s) error = actual - exact print '%-35s%-35s\t%s' % (actual, exact, error) 3602879701896397/36028797018963968 3602879701896397/36028797018963968 0 3602879701896397/18014398509481984 3602879701896397/18014398509481984 0 1351079888211149/4503599627370496 10808639105689191/36028797018963968 1/36028797018963968 3602879701896397/9007199254740992 14411518807585589/36028797018963968 -1/36028797018963968 1/2 18014398509481985/36028797018963968 -1/36028797018963968 5404319552844595/9007199254740992 21617278211378381/36028797018963968 -1/36028797018963968 3152519739159347/4503599627370496 25220157913274777/36028797018963968 -1/36028797018963968 7205759403792793/9007199254740992 28823037615171173/36028797018963968 -1/36028797018963968 2026619832316723/2251799813685248 32425917317067569/36028797018963968 -1/36028797018963968 9007199254740991/9007199254740992 36028797018963965/36028797018963968 -1/36028797018963968 Hope this helps your slides, Raymond -- http://mail.python.org/mailman/listinfo/python-list
Re: Python as a scripting language. Alternative to bash script?
On Wed, Jul 7, 2010 at 8:31 AM, Michael Torrie torr...@gmail.com wrote: On 07/06/2010 09:34 PM, Chris Rebert wrote: On Tue, Jul 6, 2010 at 6:40 AM, Michael Torrie torr...@gmail.com wrote: While it's possible to set up pipes and spawn programs in parallel to operate on the pipes, in practice it's simpler to tell subprocess.Popen to use a shell and then just rely on Bash's very nice syntax for setting up the pipeline. Until there's a Python variable involved that is, unless you want to overlook all the edge cases or do the escaping all by yourself (and then pray you did it right). Very good point. This is a problem that the pipes module suffers from as well. Although we learned in the other thread on escaping SQL statements that escaping is faster, easier and just as safe as other parameterization mechanisms. Uh huh. Back on target, a library similar to pipes that was safe (pipes is not) and had a pythonic syntax would be cool. pipes module works alright, syntax wise, but it's not a clean syntax. Actually, your original post inspired me to take a crack at writing something like that yesterday: http://rebertia.com/code/subproc_pipelines.py Thoughts anyone? (Written on a whim, so no tests or docs at present.) Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Is This Open To SQL Injection?
Hi;
I have this code:
sql = 'insert into personalDataKeys values (%s, %s, %s)' % (store, user,
', %s'.join('%s' * len(col_vals))
cursor.execute(sql, col_vals)
Is this open to injection attacks? If so, how correct?
TIA,
beno
--
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Re: Is This Open To SQL Injection?
On 7/7/10 11:38 AM, Victor Subervi wrote:
Hi;
I have this code:
sql = 'insert into personalDataKeys values (%s, %s, %s)' % (store,
user, ', %s'.join('%s' * len(col_vals))
cursor.execute(sql, col_vals)
First, its always best to be explicit with insert statements. Meaning,
don't rely on the underlining structure of a table, as in:
INSERT INTO YourRandomTable VALUES (my, value, here);
Instead, do:
INSERT INTO YourRandomTable (field1, field2, field3) VALUES (my,
value, here);
Is this open to injection attacks? If so, how correct?
Secondly, I'd say: probably yes. Maybe. You're doing string formatting
to construct your SQL, which is where the trouble comes from. Its
possible to do safely, but takes exquisite care -- which is why we've
been nudging you away from it.
But I can't be a whole lot more specific because I can't for the life of
me figure out what you're actually doing with it.
I can't figure out why you're passing the store and user variables into
the SQL statement, instead of just passing them into the .execute as you
are supposed to. I.e., cursor.execute(sql, [store, user] + col_vals) or
something.
It looks like you're sort of trying to get one generic SQL statement
which can set some arbitrary number of random columns-- if so, why? I
can't picture just what this table layout is or what kind of data it
holds to advise better.
--
Stephen Hansen
... Also: Ixokai
... Mail: me+list/python (AT) ixokai (DOT) io
... Blog: http://meh.ixokai.io/
signature.asc
Description: OpenPGP digital signature
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Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 11:32, Jonathan Hartley tart...@tartley.com wrote: Also, this would solve the pain of Python developers attempting to redistribute py2exe versions of their programs (i.e. they have to own a Visual Studio license to legally be able to redistribute the required C runtime) http://www.microsoft.com/downloads/details.aspx?FamilyID=9b2da534-3e03-4391-8a4d-074b9f2bc1bfdisplaylang=en If this is not sufficient, ask Microsoft for permission or buy a copy of Visual Studio (any will do, you can rebuild Python). I don't understand enough to know why Visual Studio was chosen instead of MinGW. Can anyone shed any light on that decision? It the standard C and C++ compiler on Windows. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
Python 3.1.1, file [pymem.h]: PyAPI_FUNC(void *) PyMem_Malloc(size_t); #define PyMem_MALLOC(n)(((n) 0 || (n) PY_SSIZE_T_MAX) ? NULL \ : malloc((n) ? (n) : 1)) The problem with the latter that it seems that it's intended for safety but does the opposite... Why do you say that? It certainly *does* achieve safety, wrt. to certain errors, specifically: - passing sizes that are out-of-range - supporting malloc(0) on all systems Perhaps (if it isn't intentional) this is a bug of the oversight type, that nobody remembered to update the macro? Update in what way? Except for the problems with file descriptors I think a practical interim solution for extensions implemented in C could be to just link the runtime lib statically. For a minimal extension this increased the size from 8 KiB to 49 KiB. And generally with MS tools the size is acceptably small. If you think that's fine for your extension module (which may well be the case), go ahead. But then, you could also just link with a different DLL version of the CRT instead. I think that this would be safe because since the C API has to access things in the interpreter I think it's a given that all the relevant functions delegate to shared library (DLL) implementations, but I have not checked the source code. There are certainly more cases than the ones mentioned so far, in particular the time zone and the locale. The CRT carries global variables for these, so if you set them in the copy of the CRT that Python links with, you won't see the change in your extension module - which may or may not be a problem. As a more longterm solution, perhaps python.org could make available the redistributables for various MSVC versions, and then one could introduce some scheme for indicating the runtime lib dependencies of any given extension. My preferred long-term solution is to reduce the usage of the C library in CPython as much as reasonable, atleast on Windows. Memory management could directly use the heap functions (or even more directly VirtualAlloc); filenos could be OS handles, and so on. There are probably limitations to what you can achieve, but I think it's worth trying. Regards, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 06:54, Alf P. Steinbach /Usenet alf.p.steinbach +use...@gmail.com wrote: PyAPI_FUNC(void *) PyMem_Malloc(size_t); #define PyMem_MALLOC(n) (((n) 0 || (n) PY_SSIZE_T_MAX) ? NULL \ : malloc((n) ? (n) : 1)) I was afraid of that :( Except for the problems with file descriptors I think a practical interim solution for extensions implemented in C could be to just link the runtime lib statically. You still have two CRTs linked into the same process. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
I presume this problem would go away if future versions of Python itself were compiled on Windows with something like MinGW gcc. Also, this would solve the pain of Python developers attempting to redistribute py2exe versions of their programs (i.e. they have to own a Visual Studio license to legally be able to redistribute the required C runtime) I don't understand enough to know why Visual Studio was chosen instead of MinGW. Can anyone shed any light on that decision? sturlamolden has already given the primary reason: Python, traditionally, attempts to use and work with the system vendor's compiler. On Windows, that's MSC. It's typically the one that best knows about platform details that other compilers might be unaware of. In addition, it's also the compiler and IDE that Windows developers (not just Python core people, but also extension developers and embedders) prefer to use, as it has quite good IDE support (in particular debugging and code browsing). Perhaps more importantly, none of the other compilers is really an alternative. GCC in particular cannot build the Win32 extensions, since it doesn't support the COM and ATL C++ features that they rely on (and may not support other MSC extensions, either). So the Win32 extensions must be built with VS, which means Python itself needs to use the same compiler. Likewise important: gcc/mingw is *not* a complete C compiler on Windows. A complete C compiler would have to include a CRT (on Windows); mingw doesn't (cygwin does, but I think you weren't proposing that Python be built for cygwin - you can easily get cygwin Python anyway). Instead, mingw relies on users having a CRT available to them - and this will be a Microsoft one. So even if gcc was used, we would have versioning issues with Microsoft CRTs, plus we would have to rely on target systems including the right CRT, as we couldn't include it in the distribution. HTH, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: Is This Open To SQL Injection?
Stephen Hansen wrote:
On 7/7/10 11:38 AM, Victor Subervi wrote:
Hi;
I have this code:
sql = 'insert into personalDataKeys values (%s, %s, %s)' % (store,
user, ', %s'.join('%s' * len(col_vals))
cursor.execute(sql, col_vals)
First, its always best to be explicit with insert statements. Meaning,
don't rely on the underlining structure of a table, as in:
INSERT INTO YourRandomTable VALUES (my, value, here);
Instead, do:
INSERT INTO YourRandomTable (field1, field2, field3) VALUES (my,
value, here);
Is this open to injection attacks? If so, how correct?
Secondly, I'd say: probably yes. Maybe. You're doing string formatting
to construct your SQL, which is where the trouble comes from. Its
possible to do safely, but takes exquisite care -- which is why we've
been nudging you away from it.
But I can't be a whole lot more specific because I can't for the life of
me figure out what you're actually doing with it.
I can't figure out why you're passing the store and user variables into
the SQL statement, instead of just passing them into the .execute as you
are supposed to. I.e., cursor.execute(sql, [store, user] + col_vals) or
something.
It looks like you're sort of trying to get one generic SQL statement
which can set some arbitrary number of random columns-- if so, why? I
can't picture just what this table layout is or what kind of data it
holds to advise better.
Not only that, there's a missing ) and the .join is wrong. For
example, if 'store' is STORE, 'user' is USER and 'col_vals' has,
say, 3 members, then what you get is:
insert into personalDataKeys values (STORE, USER, %, %ss, %s%, %ss,
%s%, %ss)
--
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Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 21:12, sturlamolden sturlamol...@yahoo.no wrote:
#define PyMem_MALLOC(n) (((n) 0 || (n) PY_SSIZE_T_MAX) ? NULL \
: malloc((n) ? (n) : 1))
I was afraid of that :(
Also observe that this macro is very badly written (even illegal) C.
Consider what this would do:
PyMem_MALLOC(n++)
According to Linus Thorvalds using macros like this is not even legal
C:
http://www.linuxfocus.org/common/src/January2004_linus.html
This would be ok, and safe as long as we use the GIL:
register Py_ssize_t __pymem_malloc_tmp;
#define PyMem_MALLOC(n)\
(__pymem_malloc_tmp = n, (((__pymem_malloc_tmp) 0 ||
(__pymem_malloc_tmp) PY_SSIZE_T_MAX) ? NULL \
: malloc((__pymem_malloc_tmp) ?
(__pymem_malloc_tmp) : 1)))
An inline function is a better solution, but not ANSI C standard:
inline void *PyMem_MALLOC(Py_ssize_t n)
{
return (((n) 0 || (n) PY_SSIZE_T_MAX) ? NULL
: malloc((n) ? (n) : 1));
}
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Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
* Martin v. Loewis, on 07.07.2010 21:10: Python 3.1.1, file [pymem.h]: PyAPI_FUNC(void *) PyMem_Malloc(size_t); #define PyMem_MALLOC(n)(((n) 0 || (n) PY_SSIZE_T_MAX) ? NULL \ : malloc((n) ? (n) : 1)) The problem with the latter that it seems that it's intended for safety but does the opposite... Why do you say that? It certainly *does* achieve safety, wrt. to certain errors, specifically: - passing sizes that are out-of-range - supporting malloc(0) on all systems It uses malloc instead of PyMem_Malloc. malloc may well be different and use a different heap in an extension DLL than in the Python interpreter and other extensions. That's one thing that the docs (rightly) warn you about. Perhaps (if it isn't intentional) this is a bug of the oversight type, that nobody remembered to update the macro? Update in what way? I was guessing that at one time there was no PyMem_Malloc. And that it was introduced to fix Windows-specific problems, but inadvertently without updating the macro. It's just a guess as to reasons why the macro uses malloc directly. Except for the problems with file descriptors I think a practical interim solution for extensions implemented in C could be to just link the runtime lib statically. For a minimal extension this increased the size from 8 KiB to 49 KiB. And generally with MS tools the size is acceptably small. If you think that's fine for your extension module (which may well be the case), go ahead. I have no comment on that except pointing it out as a somewhat stupid, somewhat evil social inclusion/exclusion argument, talking to the audience. Argh. You're wasting my time. But anyway, 49 KiB is small by today's standards. For example, you get 20 of those in a single MiB, and about 20.000 in a single GiB. But then, you could also just link with a different DLL version of the CRT instead. When I wrote link the runtime lib statically that was an alternative to the usual link-as-DLL. It wouldn't make sense to link the runtime lib statically as an alternative to linking it statically. As for linking to a different /version/ of the CRT, if you really mean that, I think that's difficult. It's not necessarily impossible, after all there's STLPort. But I think that it must at the very least be rather difficult to do with Microsoft's tools, for otherwise people would have employed that solution before, and so I wouldn't trust the result, and wouldn't waste the time trying. Cheers, - Alf -- blog at url: http://alfps.wordpress.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
* sturlamolden, on 07.07.2010 21:12: On 7 Jul, 06:54, Alf P. Steinbach /Usenetalf.p.steinbach +use...@gmail.com wrote: PyAPI_FUNC(void *) PyMem_Malloc(size_t); #define PyMem_MALLOC(n) (((n) 0 || (n) PY_SSIZE_T_MAX) ? NULL \ : malloc((n) ? (n) : 1)) I was afraid of that :( Except for the problems with file descriptors I think a practical interim solution for extensions implemented in C could be to just link the runtime lib statically. You still have two CRTs linked into the same process. So? Cheers, - Alf -- blog at url: http://alfps.wordpress.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 21:41, Alf P. Steinbach /Usenet alf.p.steinbach +use...@gmail.com wrote: You still have two CRTs linked into the same process. So? CRT resources cannot be shared across CRT borders. That is the problem. Multiple CRTs are not a problem if CRT resources are never shared. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
Also observe that this macro is very badly written (even illegal) C. Consider what this would do: PyMem_MALLOC(n++) According to Linus Thorvalds using macros like this is not even legal C: http://www.linuxfocus.org/common/src/January2004_linus.html [Please don't use legal wrt. programs - it's not illegal to violate the language's rules; you don't go to jail when doing so. Linus said not allowed] You are misinterpreting that statement. Linus said that the isdigit macro was non-conforming, *and meant that specifically for isdigit()*. That's because the C standard says that isdigit is a function. Under the as-if rule, you may implement it as a macro as long as nobody can tell the difference. However, in the presented implementation, there is a notable difference. However, the C standard is silent wrt. to PyMem_MALLOC, and it certainly allows the definition of macros which use the macro arguments more than once. This would be ok, and safe as long as we use the GIL: The macro is ok as it stands (minus the issues with multiple heaps). The Python convention is that you clearly recognize PyMem_MALLOC as a macro, so you should know not to pass parameters with side effects. register Py_ssize_t __pymem_malloc_tmp; #define PyMem_MALLOC(n)\ (__pymem_malloc_tmp = n, (((__pymem_malloc_tmp) 0 || (__pymem_malloc_tmp) PY_SSIZE_T_MAX) ? NULL \ : malloc((__pymem_malloc_tmp) ? (__pymem_malloc_tmp) : 1))) That would partially defeat the purpose, namely it would require the compiler to put the size into a variable in memory, and possibly prevent optimizations from taking place that rely on constant propagation (depending on how smart the compiler is). Regards, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 21:47, Martin v. Loewis mar...@v.loewis.de wrote: That would partially defeat the purpose, namely it would require the compiler to put the size into a variable in memory, and possibly prevent optimizations from taking place that rely on constant propagation (depending on how smart the compiler is). Also after reading carefully what Linus said, it would still be incorrect if n is a complex expression. So, an inline function is the correct one here. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
Perhaps (if it isn't intentional) this is a bug of the oversight type, that nobody remembered to update the macro? Update in what way? I was guessing that at one time there was no PyMem_Malloc. And that it was introduced to fix Windows-specific problems, but inadvertently without updating the macro. It's just a guess as to reasons why the macro uses malloc directly. It might indeed be that the function version was introduced specifically for Windows. However, the macro was left intentionally: both for backwards compatibility, and for use inside Python itself. Except for the problems with file descriptors I think a practical interim solution for extensions implemented in C could be to just link the runtime lib statically. [...] When I wrote link the runtime lib statically that was an alternative to the usual link-as-DLL. Ok, I lost the thread. When you said a practical interim solution you were talking about what problem? I thought the discussion was about the need to link with the same DLL version as Python. It wouldn't make sense to link the runtime lib statically as an alternative to linking it statically. However, it would surely make sense to link with a different DLL than the one that Python links with, assuming that would actually work. As for linking to a different /version/ of the CRT, if you really mean that, I think that's difficult. It's not necessarily impossible, after all there's STLPort. But I think that it must at the very least be rather difficult to do with Microsoft's tools, for otherwise people would have employed that solution before, and so I wouldn't trust the result, and wouldn't waste the time trying. It's actually straight-forward (or used to be, until they came up with the SxS madness). It was actually the case that people did so unexpectingly, and it seemed to work fine, except that it crashed when passing FILE*. Then we started explaining that mixing CRTs is risky. Regards, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
* sturlamolden, on 07.07.2010 21:46: On 7 Jul, 21:41, Alf P. Steinbach /Usenetalf.p.steinbach +use...@gmail.com wrote: You still have two CRTs linked into the same process. So? CRT resources cannot be shared across CRT borders. That is the problem. Multiple CRTs are not a problem if CRT resources are never shared. Yeah, but then we're down to file descriptors, C library locales and such as the remaining problems. Cheers, - Alf -- blog at url: http://alfps.wordpress.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
* Martin v. Loewis, on 07.07.2010 21:56: Perhaps (if it isn't intentional) this is a bug of the oversight type, that nobody remembered to update the macro? Update in what way? I was guessing that at one time there was no PyMem_Malloc. And that it was introduced to fix Windows-specific problems, but inadvertently without updating the macro. It's just a guess as to reasons why the macro uses malloc directly. It might indeed be that the function version was introduced specifically for Windows. However, the macro was left intentionally: both for backwards compatibility, and for use inside Python itself. Except for the problems with file descriptors I think a practical interim solution for extensions implemented in C could be to just link the runtime lib statically. [...] When I wrote link the runtime lib statically that was an alternative to the usual link-as-DLL. Ok, I lost the thread. When you said a practical interim solution you were talking about what problem? I thought the discussion was about the need to link with the same DLL version as Python. The main problem that the required MSVC redistributables are not necessarily present on the end user's system. It wouldn't make sense to link the runtime lib statically as an alternative to linking it statically. However, it would surely make sense to link with a different DLL than the one that Python links with, assuming that would actually work. As for linking to a different /version/ of the CRT, if you really mean that, I think that's difficult. It's not necessarily impossible, after all there's STLPort. But I think that it must at the very least be rather difficult to do with Microsoft's tools, for otherwise people would have employed that solution before, and so I wouldn't trust the result, and wouldn't waste the time trying. It's actually straight-forward (or used to be, until they came up with the SxS madness). It was actually the case that people did so unexpectingly, and it seemed to work fine, except that it crashed when passing FILE*. Then we started explaining that mixing CRTs is risky. Oh. Well then. :-) Cheers, - Alf -- blog at url: http://alfps.wordpress.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Is This Open To SQL Injection?
On 07/07/2010 19:38, Victor Subervi wrote:
Hi;
I have this code:
sql = 'insert into personalDataKeys values (%s, %s, %s)' % (store,
user, ', %s'.join('%s' * len(col_vals))
cursor.execute(sql, col_vals)
Is this open to injection attacks? If so, how correct?
TIA,
beno
Yes, it is trivially open to injection attacks.
What would happen if someone enters the next line into one of your col_vals
x,y);DROP DATABASE personalDataKeys; ha ha
Your sql statement would be closed early by the semicolon, and the DROP
TABLE personalDataKeys is then executed and would cause some unexpected
data loss.
Things could be more serious - DROP DATABASE mysql; for a mysql
installation for example.
You must always always every time and without any exceptions
what-so-ever, put all and every piece of data that comes from outside
the program through the appropriate routine to make whatever has been
entered into storable data and not part of the sql statement.
In php this is mysql_real_escape_string(). In your favourite language
there will be an equivalent.
If you miss just one occurrence its like leaving the side window
unlocked! Someone will get in one day.
Regards
Ian
p.s. Did I mention that there are no exceptions to the sanitise every
piece of data rule?
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Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 21:47, Martin v. Loewis mar...@v.loewis.de wrote: However, the C standard is silent wrt. to PyMem_MALLOC, and it certainly allows the definition of macros which use the macro arguments more than once. Ok, I knew there was something odd here. PyMem_Malloc is indeed a function, whilst PyMem_MALLOC is a deprecated macro. :) -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 2010-07-07, Martin v. Loewis mar...@v.loewis.de wrote: Also observe that this macro is very badly written (even illegal) C. Consider what this would do: PyMem_MALLOC(n++) According to Linus Thorvalds using macros like this is not even legal C: http://www.linuxfocus.org/common/src/January2004_linus.html [Please don't use legal wrt. programs - it's not illegal to violate the language's rules; you don't go to jail when doing so. Linus said not allowed] Nonsense. The world illegal doesn't mean you'll go to jail. Legal and illegal are used to indicate conformance or nonconformace with respect to some set of rules -- be they a programming language standard, FIFA footbal rules, or Forumula 1 technical regulations. It's perfectly standard usage to refer to an illegal forward pass in American football, to illegal tires used during a race, or to an illegal operation in a program. -- Grant Edwards grant.b.edwardsYow! I feel like I'm at in a Toilet Bowl with a gmail.comthumbtack in my forehead!! -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
Yeah, but then we're down to file descriptors, C library locales and such as the remaining problems. Don't forget errno! Every CRT might have its own errno thread local. I don't know how its handled on Windows but I suspect it suffers from the same problem. Christia -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 22:26, Christian Heimes li...@cheimes.de wrote: Don't forget errno! Every CRT might have its own errno thread local. I don't know how its handled on Windows but I suspect it suffers from the same problem. The Windows API errno is GetLastError. But a delinquent CRT might map GetLastError() to other integers. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
The main problem that the required MSVC redistributables are not necessarily present on the end user's system. It's not a problem for Python anymore. It took a while to sort all problems out. Martin and other developers have successfully figured out how to install the CRT for system wide and local user installations. A system wide installation installs the CRT in the side by side cache (WinSxS). A local installation keeps the msvcrt90.dll and the Microsoft.VC90.CRT.manifest next to the python.exe. Python extensions no longer embed a manifest so they share the CRT from the python.exe process. In order to ship a standalone exe you have to keep the CRT next to your exe. This should work for py2exe binaries as well. At our company we install our application stack entirely from subversion including Python 2.6.5, Sun JRE and lots of other stuff. This works perfectly fine for us even for servers without the MSVCRT redistributable. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Jul 7, 1:31 am, Paul McGuire pt...@austin.rr.com wrote: On Jul 6, 3:30 am, David Cournapeau courn...@gmail.com wrote: On Tue, Jul 6, 2010 at 4:30 AM, D'Arcy J.M. Cain da...@druid.net wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. This is exactly how I felt about my support for pyparsing, that I was trying continue to provide support for 2.3 users, up through 3.x users, with a single code base. (This would actually have been possible if I had been willing to introduce a performance penalty for Python 2 users, but performance is such a critical issue for parsing I couldn't justify it to myself.) This meant that I had to constrain my implementation, while trying to incorporate forward-looking support features (such as __bool__ and __dir__), which have no effect on older Python versions, but support additions in newer Pythons. I just couldn't get through on the python-dev list that I couldn't just upgrade my code to 2.6 and then use 2to3 to keep in step across the 2-3 chasm, as this would leave behind my faithful pre-2.6 users. Here are some of the methods I used: - No use of sets. Instead I defined a very simple set simulation using dict keys, which could be interchanged with set for later versions. - No generator expressions, only list comprehensions. - No use of decorators. BUT, pyparsing includes a decorator method, traceParseAction, which can be used by users with later Pythons as @traceParseAction in their own code. - No print statements. As pyparsing is intended to be an internal module, it does no I/O as part of its function - it only processes a given string, and returns a data structure. - Python 2-3 compatible exception syntax. This may have been my trickiest step. The change of syntax for except from except ExceptionType, ex: to: except ExceptionType as ex: is completely forward and backward incompatible. The workaround is to rewrite as: except ExceptionType: ex = sys.exc_info()[0] which works just fine in 2.x and 3.x. However, there is a slight performance penalty in doing this, and pyparsing uses exceptions as part of its grammar success/failure signalling and backtracking; I've used this technique everywhere I can get away with it, but there is one critical spot where I can't use it, so I have to keep 2 code bases with slight differences between them. - Implement __bool__, followed by __nonzero__ = __bool__. This will give you boolean support for your classes in 2.3-3.1. - Implement __dir__, which is unused by old Pythons, but supports customization of dir() output for your own classes. - Implement __len__, __contains__, __iter__ and __reversed__ for container classes. - No ternary expressions. Not too difficult really, there are several well-known workarounds for this, either by careful use of and's and or's, or using the bool-as-int to return the value from (falseValue,trueValue)[condition]. - Define a version-sensitive portion of your module, to define synonyms for constants that changed name between versions. Something like: _PY3K = sys.version_info[0] 2 if _PY3K: _MAX_INT = sys.maxsize basestring = str _str2dict = set alphas = string.ascii_lowercase + string.ascii_uppercase else: _MAX_INT = sys.maxint range = xrange _str2dict = lambda strg : dict( [(c,0) for c in strg] ) alphas = string.lowercase + string.uppercase The main body of my code uses range throughout (for example), and with this definition I get the iterator behavior of xrange regardless of Python version. In the end I still have 2 source files, one for Py2 and one for Py3, but there is only a small and manageable number of differences between them, and I expect at some point I will move forward to supporting Py3 as my primary target version. But personally I think this overall Python 2-3 migration process is moving along at a decent rate, and I should be able to make my switchover in another 12-18 months. But in the meantime, I am still able to support all versions of Python NOW, and I plan to continue doing so (albeit support for 2.x versions will eventually mean continue to offer a frozen feature set, with minimal bug-fixing if any). I realize that pyparsing is a simple-minded module in comparison to others: it is pure Python, so it has no issues with C extensions; it does no I/O, so print-as-statement vs. print-as-function is not an issue; and it imports few other modules, so the ones it does have not been dropped in Py3; and
Fascinating interview by Richard Stallman on Russia TV
Democracy is sick in the US, government monitors your Internet http://www.youtube.com/watch?v=2BfCJq_zIdkfeature=fvsr Enjoy . -- http://mail.python.org/mailman/listinfo/python-list
Fascinating interview by Richard Stallman on Russia TV
Democracy is sick in the US, government monitors your Internet http://www.youtube.com/watch?v=2BfCJq_zIdkfeature=fvsr Enjoy . -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. The entire fact that 3.x was *designed* to be incompatible should tell you that supporting 2.x and 3.x with a single code base is a bad idea, except for the very smallest of projects. This is the point where a project should fork and provide two different versions. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
* Christian Heimes, on 07.07.2010 22:47: The main problem that the required MSVC redistributables are not necessarily present on the end user's system. It's not a problem for Python anymore. It took a while to sort all problems out. Martin and other developers have successfully figured out how to install the CRT for system wide and local user installations. A system wide installation installs the CRT in the side by side cache (WinSxS). A local installation keeps the msvcrt90.dll and the Microsoft.VC90.CRT.manifest next to the python.exe. Python extensions no longer embed a manifest so they share the CRT from the python.exe process. In order to ship a standalone exe you have to keep the CRT next to your exe. This should work for py2exe binaries as well. At our company we install our application stack entirely from subversion including Python 2.6.5, Sun JRE and lots of other stuff. This works perfectly fine for us even for servers without the MSVCRT redistributable. I think you're talking about a different problem. The CRT installed along with CPython works for extensions using the MSVC 9.0 CRT. However developing an extension with MSVC 10 the extension will use the 10.0 CRT, which is not necessarily present on the end user's system. As I see it there are five solutions with different trade-offs: A Already having Visual Studio 2008 (MSVC 9.0), or coughing up the money for an MSDN subscription, or visiting trade shows, so as to obtain that compiler version. - Not an option for everybody. B Linking the CRT statically. - Increased size, problems with CRT state such as file descriptors. C Linking the CRT dynamically and bundling the MSVC redistributables with the extension. - Even more increased size for the download, but smaller total footprint for extensions in sum; same CRT state problems. D Linking the CRT dynamically and providing an optional download and install of the redistributables if they're not present. This would best be done with some support from the Python installation machinery. - Small nice size for extensions, still same CRT state problems. E As D + a new compiler-independent native code interface that does not carry dependencies on CRT state such as file descriptors, like JNI. - Really huge effort, and cannot be applied until some new Python version. And I think the clue here is that the CRT state problems can be avoided by careful coding. Hence, for those who cannot do A I think B is a realistic practical option, and D would be nice... Cheers, - Alf -- blog at url: http://alfps.wordpress.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Recommend a MySQLdb Forum
On 2010-07-07, Philip Semanchuk phi...@semanchuk.com wrote: On Jul 6, 2010, at 3:16 PM, Tim Johnson wrote: Greetings: I would appreciate it if some could recommend a MySQLdb forum. The one associated the sourceforge project seems like a good bet. 1) go here: http://sourceforge.net/projects/mysql-python/ 2) click support Thanks Philip -- Tim tim at johnsons-web.com or akwebsoft.com http://www.akwebsoft.com -- http://mail.python.org/mailman/listinfo/python-list
Re: SMTPHandler and Unicode
Well, you could use an approach like the one suggested here: http://plumberjack.blogspot.com/2010/07/using-custom-formatter-to-dea... That's nice, thanks. I'll use something like this. Just a thought : I will use errors=replace in the call to the encode method to be sure that the logger does not raise any exception. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
Am 07.07.2010 22:35, schrieb sturlamolden:
On 7 Jul, 22:26, Christian Heimes li...@cheimes.de wrote:
Don't forget errno! Every CRT might have its own errno thread local. I
don't know how its handled on Windows but I suspect it suffers from the
same problem.
The Windows API errno is GetLastError. But a delinquent CRT might
map GetLastError() to other integers.
Please check the source before posting. msvcrt defines errno as
_CRTIMP extern int * __cdecl _errno(void);
#define errno (*_errno())
where _errno is (see dosmap.c)
int * __cdecl _errno(void)
{
_ptiddata ptd = _getptd_noexit();
if (!ptd) {
return ErrnoNoMem;
} else {
return ( ptd-_terrno );
}
}
where _getptd_noexit returns the CRT's per-thread data (see tidtable.c).
So it *is* a mapping to other integers, and, even though it's called
dosmap.c, it is maintained because of the (limited) POSIX support in the
CRT. In particular, there is a mapping between GetLastError values and
errno values that can't be implemented through simple defines
(e.g. both ERROR_FILE_NOT_FOUND and ERROR_PATH_NOT_FOUND map to ENOENT).
In addition, a standard C implementation can rely on only certain APIs
changing errno, which MS perhaps might not be able to guarantee for
GetLastError values in exactly the same manner.
So with the way the Windows API is defined, a C implementation has no
alternative but to be delinquent.
Regards,
Martin
--
http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
* Alf P. Steinbach /Usenet, on 07.07.2010 23:19: However developing an extension with MSVC 10 the extension will use the 10.0 CRT, which is not necessarily present on the end user's system. As I see it there are five solutions with different trade-offs: A Already having Visual Studio 2008 (MSVC 9.0), or coughing up the money for an MSDN subscription, or visiting trade shows, so as to obtain that compiler version. - Not an option for everybody. B Linking the CRT statically. - Increased size, problems with CRT state such as file descriptors. C Linking the CRT dynamically and bundling the MSVC redistributables with the extension. - Even more increased size for the download, but smaller total footprint for extensions in sum; same CRT state problems. D Linking the CRT dynamically and providing an optional download and install of the redistributables if they're not present. This would best be done with some support from the Python installation machinery. - Small nice size for extensions, still same CRT state problems. E As D + a new compiler-independent native code interface that does not carry dependencies on CRT state such as file descriptors, like JNI. - Really huge effort, and cannot be applied until some new Python version. And I think the clue here is that the CRT state problems can be avoided by careful coding. Hence, for those who cannot do A I think B is a realistic practical option, and D would be nice... Wait... F Possibly, as the docs say, Developer Studio will throw in a lot of import libraries that you do not really need, adding about 100K to your executable. To get rid of them, use the Project Settings dialog, Link tab, to specify ignore default libraries. Add the correct msvcrtxx.lib to the list of libraries. Can anyone confirm whether this works in practice with MSVC 10? Cheers, - Alf -- blog at url: http://alfps.wordpress.com -- http://mail.python.org/mailman/listinfo/python-list
Storing a callback function as a class member
Hi, I have a class, where I want to store a callback function as a member to access later: class CallbackClass: def setCallback(self,cb): self.cb = cb def callCallback(self, para): self.cb(para) Doing so, I get the error: callbackFunc() takes exactly 1 parameter (2 given) self is given as parameter this way, is it not? How can this be done? Thanks! Nathan -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 23:33, Martin v. Loewis mar...@v.loewis.de wrote: The Windows API errno is GetLastError. But a delinquent CRT might map GetLastError() to other integers. Please check the source before posting. msvcrt defines errno as I don't have the source to msvcrt, at least not to my knowledge. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
Am 07.07.2010 23:49, schrieb sturlamolden: On 7 Jul, 23:33, Martin v. Loewis mar...@v.loewis.de wrote: The Windows API errno is GetLastError. But a delinquent CRT might map GetLastError() to other integers. Please check the source before posting. msvcrt defines errno as I don't have the source to msvcrt, at least not to my knowledge. If you have Visual Studio, and opted to install the CRT sources, you'll find them in VC/crt/src (or VC7/crt/src, depending on VS version). I'm not 100% sure whether they are included in VS Express as well. Regards, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
Brendan Abel wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. The entire fact that 3.x was *designed* to be incompatible should tell you that supporting 2.x and 3.x with a single code base is a bad idea, except for the very smallest of projects. This is the point where a project should fork and provide two different versions. I wouldn't say that 3.x was designed to be incompatible. It was designed to tidy the language, and the incompatibilities are an unfortunate result. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 7 Jul, 23:19, Alf P. Steinbach /Usenet alf.p.steinbach +use...@gmail.com wrote: D Linking the CRT dynamically and providing an optional download and install of the redistributables if they're not present. This would best be done with some support from the Python installation machinery. - Small nice size for extensions, still same CRT state problems. This was a problem for py2exe'd apps before Python 2.6 (i.e. no public download for Visual C++ 2003 runtime files.) But for Visual C++ 2008 and 2010, the CRTs can be downloaded from Microsoft and need not be shipped with the application. http://www.microsoft.com/downloads/details.aspx?familyid=9B2DA534-3E03-4391-8A4D-074B9F2BC1BFdisplaylang=en http://www.microsoft.com/downloads/details.aspx?familyid=BA9257CA-337F-4B40-8C14-157CFDFFEE4Edisplaylang=en http://www.microsoft.com/downloads/details.aspx?FamilyID=a7b7a05e-6de6-4d3a-a423-37bf0912db84displaylang=en http://www.microsoft.com/downloads/details.aspx?familyid=BD512D9E-43C8-4655-81BF-9350143D5867displaylang=en -- http://mail.python.org/mailman/listinfo/python-list
How to test/troubshoot an extension (pylibconfig)?
I'm trying to use python bindings for libconfig. There appear to be three very slightly different bindings: http://code.google.com/p/python-libconfig/ http://wiki.github.com/cnangel/python-libconfig/ http://github.com/azeey/python-libconfig/ I'm using the latter with libconfig 1.4.5 http://www.hyperrealm.com/libconfig/ The python bindings appear to come with test cases, but I can't figure out how to run them. From reading the Python docs, it would appear that this should do something useful, but it doesn't: $ python -m unittest pylibconfig -- Ran 0 tests in 0.000s Trying to run the test script directory doesn't work either: $ python tests/test.py Traceback (most recent call last): File tests/test.py, line 8, in module from x64.pylibconfig import Config ImportError: No module named x64.pylibconfig Importing the module seems to be OK, but creating an instance barfs: Python 2.6.5 (release26-maint, Jun 22 2010, 12:58:11) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. import pylibconfig conf = pylibconfig.Config() *** glibc detected *** /usr/bin/python2.6: corrupted double-linked list: 0x08065c48 *** Where to go from here? -- Grant Edwards grant.b.edwardsYow! Do you like TENDER at VITTLES? gmail.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing a callback function as a class member
Nathan Huesken wrote: Hi, I have a class, where I want to store a callback function as a member to access later: class CallbackClass: def setCallback(self,cb): self.cb = cb def callCallback(self, para): self.cb(para) Doing so, I get the error: callbackFunc() takes exactly 1 parameter (2 given) self is given as parameter this way, is it not? How can this be done? Could you provide a short program which we could run to reproduce the problem? -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion
John Nagle na...@animats.com writes: Python 3 is a nice cleanup of some legacy syntax issues. But that's just not enough. Perl 6 is a nice cleanup of Perl 5, Eh, I wouldn't call Perl 6 a nice cleanup. It's much better to consider it a new language with roots in Perl 5 (amongst others). Or to quote from http://dev.perl.org/perl6/: Perl 5 and Perl 6 are two languages in the Perl family, but of different lineages. and look how that went. Ten years on, it's not even mainstream, let alone dominant. I don't think that's the point of Perl 6 (if one can even say such a thing, that is). Right now, (I) think of Perl 6 as a test bed for features that couldn't be put in Perl 5 in an easy manner. Or (I) think of it as a programming language lab. My best guess is that with coming Christmas there will be a Perl 6 comparable to Python 3. But huge disclaimer: I hardly follow Perl 6 development. -- John Bokma j3b Hacking Hiking in Mexico - http://johnbokma.com/ http://castleamber.com/ - Perl Python Development -- http://mail.python.org/mailman/listinfo/python-list
Re: How to test/troubshoot an extension (pylibconfig)?
On 2010-07-07, Grant Edwards inva...@invalid.invalid wrote: I'm trying to use python bindings for libconfig. There appear to be three very slightly different bindings: http://code.google.com/p/python-libconfig/ http://wiki.github.com/cnangel/python-libconfig/ http://github.com/azeey/python-libconfig/ I'm using the latter with libconfig 1.4.5 http://www.hyperrealm.com/libconfig/ [...] Importing the module seems to be OK, but creating an instance barfs: Python 2.6.5 (release26-maint, Jun 22 2010, 12:58:11) [GCC 4.3.4] on linux2 Type help, copyright, credits or license for more information. import pylibconfig conf = pylibconfig.Config() *** glibc detected *** /usr/bin/python2.6: corrupted double-linked list: 0x08065c48 *** Oops. Those Python bindings are for version 1.3.2 of libconfig (which does work). They don't work with the current version of libconfig. I guess it's time to figure out how boost works... -- Grant Edwards grant.b.edwardsYow! ... I think I'd at better go back to my DESK gmail.comand toy with a few common MISAPPREHENSIONS ... -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing a callback function as a class member
On Wed, 07 Jul 2010 22:48:11 +0100, Nathan Huesken pyt...@lonely-star.org wrote: Hi, I have a class, where I want to store a callback function as a member to access later: class CallbackClass: def setCallback(self,cb): self.cb = cb def callCallback(self, para): self.cb(para) Doing so, I get the error: callbackFunc() takes exactly 1 parameter (2 given) self is given as parameter this way, is it not? How can this be done? rho...@gnudebst:~$ python Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41) [GCC 4.4.3] on linux2 Type help, copyright, credits or license for more information. class CBClass: ... def set_cb(self, cb): ... self.cb = cb ... def call_cb(self, para): ... self.cb(para) ... def trivial(arg): ... print arg ... c = CBClass() c.set_cb(trivial) c.call_cb(Hello, world) Hello, world Works for me. Which version of Python are you using? -- Rhodri James *-* Wildebeeste Herder to the Masses -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing a callback function as a class member
On 7/7/2010 2:48 PM Nathan Huesken said... class CallbackClass: def setCallback(self,cb): self.cb = cb def callCallback(self, para): self.cb(para) You'll have to show how you're invoking this -- the following works for me (ie, I don't get an error): class CallbackClass: def setCallback(self,cb): self.cb = cb def callCallback(self, para): self.cb(para) a = CallbackClass() def test(param): return 2*param a.setCallback(test) a.callCallback(3) Emile -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On Jul 7, 8:22 pm, Martin v. Loewis mar...@v.loewis.de wrote: I presume this problem would go away if future versions of Python itself were compiled on Windows with something like MinGW gcc. Also, this would solve the pain of Python developers attempting to redistribute py2exe versions of their programs (i.e. they have to own a Visual Studio license to legally be able to redistribute the required C runtime) I don't understand enough to know why Visual Studio was chosen instead of MinGW. Can anyone shed any light on that decision? sturlamolden has already given the primary reason: Python, traditionally, attempts to use and work with the system vendor's compiler. On Windows, that's MSC. It's typically the one that best knows about platform details that other compilers might be unaware of. In addition, it's also the compiler and IDE that Windows developers (not just Python core people, but also extension developers and embedders) prefer to use, as it has quite good IDE support (in particular debugging and code browsing). Perhaps more importantly, none of the other compilers is really an alternative. GCC in particular cannot build the Win32 extensions, since it doesn't support the COM and ATL C++ features that they rely on (and may not support other MSC extensions, either). So the Win32 extensions must be built with VS, which means Python itself needs to use the same compiler. Likewise important: gcc/mingw is *not* a complete C compiler on Windows. A complete C compiler would have to include a CRT (on Windows); mingw doesn't (cygwin does, but I think you weren't proposing that Python be built for cygwin - you can easily get cygwin Python anyway). Instead, mingw relies on users having a CRT available to them - and this will be a Microsoft one. So even if gcc was used, we would have versioning issues with Microsoft CRTs, plus we would have to rely on target systems including the right CRT, as we couldn't include it in the distribution. HTH, Martin I see. Thanks very much to both of you for the info, much appreciated. -- http://mail.python.org/mailman/listinfo/python-list
Re: Download Microsoft C/C++ compiler for use with Python 2.6/2.7 ASAP
On 8 Jul, 00:35, Jonathan Hartley tart...@tartley.com wrote: I see. Thanks very much to both of you for the info, much appreciated. The problem you referred to for py2exe despaired with Python 2.6. For Python 2.5, there was no public download option for msvcr71.dll and msvcp71.dll. There was also the unsolved SxS issue. Thus a license for Visual Studio 2003 was required to distribute py2exe apps for Python 2.5. That is now history. For py2exe apps using Python 2.6, 2.7 or 3.1, you can just ask your clients to install this: http://www.microsoft.com/downloads/details.aspx?familyid=9B2DA534-3E03-4391-8A4D-074B9F2BC1BFdisplaylang=en http://www.microsoft.com/downloads/details.aspx?familyid=BA9257CA-337F-4B40-8C14-157CFDFFEE4Edisplaylang=en There are similar downloads for Visual C++ 2010 run-time files as well. Python 3.2 will probably be built with Visual Studio 2010. -- http://mail.python.org/mailman/listinfo/python-list
Re: Argh! Name collision!
On Tuesday 06 July 2010 22:42:25 rantingrick wrote: On Jul 6, 9:11 pm, Alf P. Steinbach /Usenet alf.p.steinbach +use...@gmail.com wrote: pyni! Pronounced like tiny! Yay! hmm, how's about an alternate spelling... pyknee, or pynee, or pynie ... considering those are not taken either? Pynie's taken too -- it's the Python implementation on the Parrot VM. Rami Chowdhury As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one. -- Godwin's Law +1-408-597-7068 / +44-7875-841-046 / +88-01819-245544 -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
On 7 Jul., 19:32, Ethan Furman et...@stoneleaf.us wrote: Nobody wrote: On Wed, 07 Jul 2010 15:08:07 +0200, Thomas Jollans wrote: you should never rely on a floating-point number to have exactly a certain value. Never is an overstatement. There are situations where you can rely upon a floating-point number having exactly a certain value. It's not much of an overstatement. How many areas are there where you need the number 0.155511151231257827021181583404541015625000? If I'm looking for 0.1, I will *never* (except by accident ;) say if var == 0.1: it'll either be = or =. The following is an implementation of a well-known algorithm. Why would you want to replace the floating point comparisons? With what? (This is toy-code.) # from random import random def min_cost_path(cost_right, cost_up): return minimal cost and its path in a rectangle - going up and right only cost = dict() size_x, size_y = max(cost_right) #compute minimal cost cost[0, 0] = 0.0 for x in range(size_x): cost[x + 1, 0] = cost[x, 0] + cost_right[x, 0] for y in range(size_y): cost[0, y + 1] = cost[0, y] + cost_up[0, y] for x in range(size_x): cost[x + 1, y + 1] = min(cost[x, y + 1] + cost_right[x, y + 1], cost[x + 1, y] + cost_up[x + 1, y]) #compute path (reversed) x = size_x y = size_y path = [] while x != 0 and y != 0: if x == 0: y -= 1 path.append(u) elif y == 0: x -= 1 path.append(r) elif cost[x - 1, y] + cost_right[x - 1, y] == cost[x, y]: # fp compare x -= 1 path.append(r) elif cost[x, y - 1] + cost_up[x, y - 1] == cost[x, y]: # fp compare y -= 1 path.append(u) else: raise ValueError return cost[size_x, size_y], .join(reversed(path)) if __name__ == __main__: size = 100 cost_right = dict(((x, y), random()) for x in range(size) for y in range(size)) cost_up = dict(((x, y), random()) for x in range(size) for y in range(size)) print min_cost_path(cost_right, cost_up) -- http://mail.python.org/mailman/listinfo/python-list
Re: Argh! Name collision!
Rami Chowdhury wrote: On Tuesday 06 July 2010 22:42:25 rantingrick wrote: On Jul 6, 9:11 pm, Alf P. Steinbach /Usenet alf.p.steinbach +use...@gmail.com wrote: pyni! Pronounced like tiny! Yay! hmm, how's about an alternate spelling... pyknee, or pynee, or pynie ... considering those are not taken either? Pynie's taken too -- it's the Python implementation on the Parrot VM. PyNatInt gets no hits on Google. -- http://mail.python.org/mailman/listinfo/python-list
Re: delegation pattern via descriptor
On Jul 7, 2:46 am, Bruno Desthuilliers
bdesth.quelquech...@free.quelquepart.fr wrote:
Gregory Ewing a écrit :
Bruno Desthuilliers wrote:
kedra marbun a écrit :
if we limit our discussion to py:
why __{get|set|delete}__ don't receive the 'name' 'class' from
__{getattribute|{set|del}attr}__
'name' is the name that is searched
While it would have been technically possible, I fail to imagine any use
case for this.
I think he wants to have generic descriptors that are
shared between multiple attributes, but have them do
different things based on the attribute name.
I already understood this, but thanks !-)
What I dont understand is what problem it could solve that couldn't be
solved more simply using the either _getattr__ hook or hand-coded
delegation, since such a descriptor would be so tightly coupled to the
host class that it just doesn't make sense writing a descriptor for this.
yeah, i finally can agree descriptor isn't supposed to be used as
delegation in general, it should be the job of __getattr__
however i still think passing name would open up some other
possibilities of use (not necessarily on the basis of sharing
descriptor), surely some of them (all of it?) are bad. sure as hell,
my example is an example of bad use. for now, i conclude that passing
name is too risky, it easily allows bad practices particularly against
the law of Demeter
thanks Bruno
btw, is there a common approach to let the interface of a class that
uses __getattr__, to include names that are delegated?
class A:
def do_this(self): ...
class B:
a = A()
def do_that(self): ...
def __getattr__(self, name):
try:
return types.MethodType(getattr(self.a, name), self)
except AttributeError:
raise AttributeError
how to make 'dir(B)' includes 'do_this', do i have to use __dir__? and
if i use __dir__, somewhat 'help(B)' doesn't work as usual, i haven't
check pydoc.py ;)
--
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Re: Getting pyparsing to backtrack
I'm working on street address parsing again, and I'm trying to deal with some of the harder cases. For yet another test case my actual address includes ... East South Mountain Avenue Sometimes written as ... E. South Mtn Ave -- Stanley C. Kitching Human Being Phoenix, Arizona -- http://mail.python.org/mailman/listinfo/python-list
Re: Argh! Name collision!
* rantingrick, on 07.07.2010 07:42:
On Jul 6, 9:11 pm, Alf P. Steinbach /Usenetalf.p.steinbach
+use...@gmail.com wrote:
pyni! Pronounced like tiny! Yay!
hmm, how's about an alternate spelling... pyknee, or pynee, or
pynie ... considering those are not taken either?
Hm, for pure shock value I think I'll use the acronym PYthon Native Interface
Support.
pynis! :-)
A set of C++ classes to ease the writing of extensions.
Like,
code file=Ptr.h
// progrock.pynis -- Python Native Interface Support
// A simple C++ framework for writing Python 3.x extensions.
//
// Copyright (C) Alf P. Steinbach, 2010.
#ifndef PYNIS_PTR_H
#define PYNIS_PTR_H
#include progrock/cppx/devsupport/better_experience.h
//- Dependencies:
#include Python.h
#include assert.h
#include algorithm
//- Interface:
namespace progrock{ namespace pynis {
enum DoAddRef { doAddRef };
class Ptr
{
private:
PyObject* p_;
public:
Ptr( PyObject* p = 0 ): p_( p )
{}
Ptr( PyObject* p, DoAddRef ): p_( p )
{
assert( p != 0 );
Py_INCREF( p_ );
}
Ptr( Ptr const other ): p_( other.p_ )
{
Py_XINCREF( p_ );
}
~Ptr()
{
Py_XDECREF( p_ );
}
void swapWith( Ptr other ) { std::swap( p_, other.p_ ); }
Ptr operator=( Ptr other ) { swapWith( other ); return *this; }
PyObject* get() const { return p_; }
PyObject* release()
{
PyObject* const result = p_;
Py_XDECREF( p_ );
p_ = 0;
return result;
}
};
} } // namespace progrock::pynis
#endif
/code
Cheers,
- Alf (shocked)
PS: Darn, forgot to google it. But I think it's unlikely the name's already in
use!
--
blog at url: http://alfps.wordpress.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: delegation pattern via descriptor
On Jul 6, 12:11 pm, Steven D'Aprano steve-REMOVE-
t...@cybersource.com.au wrote:
On Mon, 05 Jul 2010 21:12:47 -0700, kedra marbun wrote:
On Jul 5, 7:49 am, Gregory Ewing greg.ew...@canterbury.ac.nz wrote:
kedra marbun wrote:
now, i'm asking another favor, what about the 2nd point in my 1st
post?
Your original post has dropped off my newsscope, so you'll have to
remind me what the 2nd point was.
--
Greg
it's like 'name', it's about info that i think should be passed to
descriptor's __{get|set|delete}__. i wonder what are the reasons for not
passing the class on which the descriptor is attached to, what pattern
is encouraged by this?
Perhaps I'm missing the context, but since the descriptor is passed the
instance, you can easily get the class with type(self) or self.__class__.
There's no need to pass the class as a separate argument.
--
Steven
no, the class that i meant is the one that actually has the descriptor
in its __dict__, not instance.__class__
the class obj that you said unecessary-as-arg is what __get__ receives
as the 3rd arg
class Desc:
def __get__(*args): print(args)
class a:
v0 = Desc()
class b(a): pass
b().v0 #(desc, b(), b)
--
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Re: Is This Open To SQL Injection?
Yes, you SQL would be trivial to manipulate via SQL injection. Not only do you need to validate each piece of data submitted by a user, you need to escape all the wildcard characters that your database uses. If the text string supplied by a user has quotes or parens or wildcard characters, the text could be interpreted as SQL and that is what you must avoid. Kee Nethery -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Jul 7, 3:00 pm, MRAB pyt...@mrabarnett.plus.com wrote: Brendan Abel wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. The entire fact that 3.x was *designed* to be incompatible should tell you that supporting 2.x and 3.x with a single code base is a bad idea, except for the very smallest of projects. This is the point where a project should fork and provide two different versions. I wouldn't say that 3.x was designed to be incompatible. It was designed to tidy the language, and the incompatibilities are an unfortunate result. You're missing the point, and arguing semantics. It's a good thing I didn't misspell anything. Python 3.x will continue to change. The incompatibilities between 3.x and 2.x will only become more numerous. If your goal is to support 2.x, and 3.x, you'd be best supporting them separately. -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing a callback function as a class member
On Wed, Jul 7, 2010 at 3:48 PM, Nathan Huesken pyt...@lonely-star.org wrote: Hi, I have a class, where I want to store a callback function as a member to access later: class CallbackClass: def setCallback(self,cb): self.cb = cb def callCallback(self, para): self.cb(para) Doing so, I get the error: callbackFunc() takes exactly 1 parameter (2 given) self is given as parameter this way, is it not? How can this be done? No, self will not be passed as a parameter. A function is only treated as a method when it is present in the class dict. If it is in the instance dict as you have above, then it's just a normal function. If you want it to receive self in this case, then you should have your callCallback method pass it in explicitly. HTH, Ian -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Wed, Jul 7, 2010 at 8:26 PM, Brendan Abel 007bren...@gmail.com wrote: On Jul 7, 3:00 pm, MRAB pyt...@mrabarnett.plus.com wrote: Brendan Abel wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. The entire fact that 3.x was *designed* to be incompatible should tell you that supporting 2.x and 3.x with a single code base is a bad idea, except for the very smallest of projects. This is the point where a project should fork and provide two different versions. I wouldn't say that 3.x was designed to be incompatible. It was designed to tidy the language, and the incompatibilities are an unfortunate result. You're missing the point, and arguing semantics. It's a good thing I didn't misspell anything. Python 3.x will continue to change. The incompatibilities between 3.x and 2.x will only become more numerous. If your goal is to support 2.x, and 3.x, you'd be best supporting them separately. I maintain two projects that have to work from 2.5 to 3.1. On one of them (~5kloc) we took the separate support route, and on the other (~30kloc) I decided to keep a single codebase. IME the maintenance burden on the former is substantially higher than the latter. Is the difference in difficulty perhaps domain-related, or a result of a certain style of coding? Could you give us some more details about what you were working on that caused you to conclude this? Geremy Condra -- http://mail.python.org/mailman/listinfo/python-list
ANN: ActivePython 2.7.0.1 is now available
We are pleased to announce the availability of ActivePython 2.7.0.1. http://www.activestate.com/activepython This release corresponds to the recently released Python 2.7, and, like ActivePython 2.6, includes the Python Package Manager (PyPM) with essential packages such as Distribute (a compatible fork of setuptools), virtualenv, pip and SQLAlchemy. See the release notes for full details: http://docs.activestate.com/activepython/2.7/relnotes.html#changes For a high-level overview of this release, please see our blog post: http://www.activestate.com/blog/2010/07/activepython-27-released This is also the first ActivePython release with 64-bit support on MacOSX. What is ActivePython? - ActivePython is ActiveState's binary distribution of Python. Builds for Windows, Mac OS X, Linux are made freely available. Solaris, HP-UX and AIX builds, and access to older versions are available in ActivePython Business, Enterprise and OEM editions: http://www.activestate.com/python ActivePython includes the Python core and the many core extensions: zlib and bzip2 for data compression, the Berkeley DB (bsddb) and SQLite (sqlite3) database libraries, OpenSSL bindings for HTTPS support, the Tix GUI widgets for Tkinter, ElementTree for XML processing, ctypes (on supported platforms) for low-level library access, and others. The Windows distribution ships with PyWin32 -- a suite of Windows tools developed by Mark Hammond, including bindings to the Win32 API and Windows COM. ActivePython 2.6 and 2.7 also include a binary package manager for Python (PyPM) that can be used to install packages much easily. For example: C:\pypm install mysql-python [...] C:\python import MySQLdb See this page for full details: http://docs.activestate.com/activepython/2.7/whatsincluded.html As well, ActivePython ships with a wealth of documentation for both new and experienced Python programmers. In addition to the core Python docs, ActivePython includes the What's New in Python series, Dive into Python, the Python FAQs HOWTOs, and the Python Enhancement Proposals (PEPs). An online version of the docs can be found here: http://docs.activestate.com/activepython/2.7/ We would welcome any and all feedback to: activepython-feedb...@activestate.com Please file bugs against ActivePython at: http://bugs.activestate.com/enter_bug.cgi?product=ActivePython On what platforms does ActivePython run? ActivePython includes installers for the following platforms: - Windows/x86 - Windows/x64 (aka AMD64) - Mac OS X - Linux/x86 - Linux/x86_64 (aka AMD64) - Solaris/SPARC (Business, Enterprise or OEM edition only) - Solaris/x86 (Business, Enterprise or OEM edition only) - HP-UX/PA-RISC (Business, Enterprise or OEM edition only) - HP-UX/IA-64 (Enterprise or OEM edition only) - AIX/PowerPC (Business, Enterprise or OEM edition only) - AIX/PowerPC 64-bit (Business, Enterprise or OEM edition only) Custom builds are available in Enterprise Edition: http://www.activestate.com/enterprise-edition Thanks, and enjoy! The Python Team -- Sridhar Ratnakumar sridharr at activestate.com -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion
geremy condra debat...@gmail.com writes: On Wed, Jul 7, 2010 at 8:26 PM, Brendan Abel 007bren...@gmail.com wrote: Python 3.x will continue to change. The incompatibilities between 3.x and 2.x will only become more numerous. If your goal is to support 2.x, and 3.x, you'd be best supporting them separately. I maintain two projects that have to work from 2.5 to 3.1. On one of them (~5kloc) we took the separate support route, and on the other (~30kloc) I decided to keep a single codebase. IME the maintenance burden on the former is substantially higher than the latter. The point, one more time with feeling, is that the incompatibilities between 2.x and 3.x will *increase* over time. If you now have a code base that is relatively easy to maintain for both Python 2.x and 3.x, that is a result of much back-porting efforts and of a new-feature moratorium that is currently in effect. Enjoy that situation as you may, because it is guaranteed not to last. Indeed, the feature moratorium is designed in part to help slow-moving codebases migrate to Python 3.x before Python resumes its normal pace of change again. If you're choosing to use that time to further entrench codebases for Python 2.x, I think that's a short-sighted choice. Python 2.7 is the last 2.x, no further 3.x features will be back-ported. New 3.x features will begin to appear after the moratorium ends. The combination of those two means that *the single-codebase burden will only increase over time* as Python 3.x diverges further from what Python 2.x can support. -- \ “Programs must be written for people to read, and only | `\incidentally for machines to execute.” —Abelson Sussman, | _o__) _Structure and Interpretation of Computer Programs_ | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
geremy condra wrote: On Wed, Jul 7, 2010 at 8:26 PM, Brendan Abel 007bren...@gmail.com wrote: On Jul 7, 3:00 pm, MRAB pyt...@mrabarnett.plus.com wrote: Brendan Abel wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. The entire fact that 3.x was *designed* to be incompatible should tell you that supporting 2.x and 3.x with a single code base is a bad idea, except for the very smallest of projects. This is the point where a project should fork and provide two different versions. I wouldn't say that 3.x was designed to be incompatible. It was designed to tidy the language, and the incompatibilities are an unfortunate result. You're missing the point, and arguing semantics. It's a good thing I didn't misspell anything. Python 3.x will continue to change. The incompatibilities between 3.x and 2.x will only become more numerous. If your goal is to support 2.x, and 3.x, you'd be best supporting them separately. I maintain two projects that have to work from 2.5 to 3.1. On one of them (~5kloc) we took the separate support route, and on the other (~30kloc) I decided to keep a single codebase. IME the maintenance burden on the former is substantially higher than the latter. Is the difference in difficulty perhaps domain-related, or a result of a certain style of coding? Could you give us some more details about what you were working on that caused you to conclude this? In my work on the regex module I use a single codebase and generate the sources for Python 2.5-2.7 and for Python 3.1 from it. It works easily enough for me. -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Jul 5, 1:34 am, sturlamolden sturlamol...@yahoo.no wrote: On 5 Jul, 01:58, John Nagle na...@animats.com wrote: Exactly. The incompatible with all extension modules I need part is the problem right now. A good first step would be to identify the top 5 or 10 modules that are blocking a move to Python 3 by major projects with many users. The big danger is Python 2.x becoming abandonware (2.7 being the final release) before major projects are ported. Using Python 2.x for new projects is not advisable (at least many will think so), and using 3.x is not possible. What to do? It's not a helpful situation for Python. But Python 2.3, 2.4 2.5 are *already* abandonware and see *major* use in many systems and businesses. Python development has always gone ahead of what *some* people use - and they don't seem to mind that they're using essentially abandoned versions of Python. Now that 2.7 is out I *might* be able to persuade my current company to migrate to 2.6 on the servers, and they're far faster at adopting tech than many companies I know. All the best, Michael Foord -- http://www.voidspace.org.uk -- http://mail.python.org/mailman/listinfo/python-list
Re: The real problem with Python 3 - no business case for conversion (was I strongly dislike Python 3)
On Jul 7, 2:10 pm, Brendan Abel 007bren...@gmail.com wrote: One thing that would be very useful is how to maintain something that works on 2.x and 3.x, but not limiting yourself to 2.6. Giving up versions below 2.6 is out of the question for most projects with a significant userbase IMHO. As such, the idea of running the python 3 warnings is not so useful IMHO - unless it could be made to work better for python 2.x 2.6, but I am not sure the idea even makes sense. The entire fact that 3.x was *designed* to be incompatible should tell you that supporting 2.x and 3.x with a single code base is a bad idea, except for the very smallest of projects. This is the point where a project should fork and provide two different versions. Well, I think it could be a reasonable thing to maintain a single codebase in 2.x and use 2to3 (and/or a custom translator) to translate to 3.x version for quite a while. For the humble library I maintain, I plan to release a Python 3 version as soon as a Python 3 version of numpy is released, maintain a single codebase (translating from 2 version to 3) for awhile, then at some point fork them and maintain them separately. Given that I add features about once every 2 years I don't think it'll be too much of a burden, though. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
