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

Not going to let this drop ...
by Steve Holden June 2, 2009

June 2, 2009

If you have a few minutes to read this message you might just be able to make a big difference to the lives of some very disadvantaged people. If you can't help, don't worry. Sorry for bothering you. There's a project that needs help. The chuzer project is moribund (the rest of this message explains what it is). I accept responsibility for that. I have had a lot on my plate recently, but everything is relative, and my information from other sources tells me that some recipients of this email have far worse problems than I. Paul McNett said in a recent email "this seems like too noble a project to die", and I agree with him. It seems to me that a really quite small amount of development time could see us producing a system that would add a huge amount to the lives of some of the most needy people we can imagine. Or not. Frankly, it's the imagining that scares me. I am having real difficulty imagining what it might be like to be in a position where I can't easily tell someone what I need. The chuzer project will allow severely disabled people to express the most basic needs. Maybe "what I want for pudding" wasn't a particularly good example, but it was the one the project was motivated by, and it's hard to think how frustrating it must be when being able to tell someone what you want for pudding represents an improvement in your quality of life. There are quadriplegics out there with such a limited range of expressive ability that the only way they can express any choice at all is to watch a series of selections tick by until the right one comes up, and then puff into a pipe or bite down on something - basically, perform one of the very few movements of which they are capable - to say "that's what I want". Yes, it might be "what I want for pudding", but how about even more basic choices: a) I need to pee b) I have to take a dump c) I am hungry d) I am thirsty e) Please hug me f) My bedsores are hurting The big problem for a lot of quadriplegics, as far as I understand it, is that uninformed people treat them as though their brains were as damaged as their bodies. Most readers of this email will be able-bodied. Please try and imagine what it would be like to be entombed in a full-body plaster cast and be unable to speak, but to still retain your full mental faculties. Don't you think you might really appreciate even something as simple as a choice program? I was intending to try and recruit assistance at PyCon, but sadly on the Saturday I received news of my mother's death, so that kind of put the kibosh on that, and I had to leave early. I also recently realized rather too late that this project would be an excellent candidate for a Google Summer of Code project, but that's already underway now. Again, I apologize for not having the time to bring chuzer to enough people's attention to get it on the GSoc radar. My bad. I don't know if Google are planning to run a Highly-Open Participation event this year, but if they are then maybe we could establish a few tasks for that. Basically this is a project that really needs some help right now. There's a basic working model, around which an image-selection and audio-recording infrastructure needs to be built so that it's easy for carers to set up appropriate choices and easy for users to indicate choices. It's not rocket science, it just needs a few of us to care enough to keep moving this project forward until it's done. It would make an excellent wxPython learning project. If anyone who reads this email has anything to offer - time, money, equipment, whatever, I'd be *really* grateful to hear from them. I can put you in touch with people who know about things like the range of interface devices available for paraplegic and quadriplegic people. Ideally the program would be adaptable to a wide range of hardware accommodating a broad spectrum of disability, but many quadriplegics use equipment that emulates a standard keyboard and/or mouse, so that would be a great start. Please help, even if only by publicizing this project. You don't even have to code, just to help with ideas for recruiting coding assistance. http://chuzer.org/ Even better, please join the mailing list linked on the site, and help to make the world a better place. regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ Watch PyCon on video now! http://pycon.blip.tv/ -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ Watch PyCon on video now! http://pycon.blip.tv/

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Re: how to get the path of a module (myself) ?
by Carl Banks June 2, 2009

June 2, 2009

On Jun 1, 4:46 pm, Stef Mientki <stef.mien...(a)gmail.com> wrote: > MRAB wrote: > > Stef Mientki wrote: > >> hello, > > >> I've pictures stored in a path relative to my python source code. > >> To get a picture, I need to know what path I'm on in each python module. > >> I thought __file__ would do the job, > >> but apparently I didn't read the documentation carefully enough, > >> because file is the path to the module that called my module. > > >> Any ways to get the path of "myself" ? > > > I'm not sure what you mean. I just did a quick test. > > > # File: C:\Quick test\child.py > > print "name is %s" % __name__ > > print "file is %s" % __file__ > > > # File: C:\Quick test\parent.py > > import child > > > print "name is %s" % __name__ > > print "file is %s" % __file__ > > > # Output: > > name is child > > file is C:\Quick test\child.py > > name is __main__ > > file is C:\Quick test\parent.py > > Yes, that's what I (and many others) thought, > but now put your code in a file, let's say the file "test.py", > and now run this file by : > execfile ( 'test.py' ) How can you execfile test.py without knowing the path to it? Whatever path you used to locate test.py is where the file is. If you're just execfiling a bare filename, then it's in the current directory, so just construct a relative pathname. Carl Banks

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Re: Python, Tkinter and popen problem
by Piet van Oostrum June 1, 2009

June 1, 2009

>>>>> norseman <norseman(a)hughes.net> (n) wrote: >n> Piet van Oostrum wrote: >>>>>>>> norseman <norseman(a)hughes.net> (n) wrote: >>> >n> I have tried both and Popen2.popen2(). >n> os.popen runs both way, contrary to docs. >>> >>> What do you mean `os.popen runs both way'? >n> It reads from child while console writes directly to child - thus >n> eliminating the problem of coding a pass through from master. Yes, but that is not `both way': popen connects the parent to the child through a pipe. The pipe works one way: from the child to the parent with 'r' (default), from the parent to the child with 'w'. You can't communicate the other way through the pipe. So the communication from the parent process to the child through the popen is ONE WAY. If you want TWO WAY communication you can use popen2, or better use subprocess.Popen. A child process always inherits stdin, stdout and stderr from the parent unless you change that (e.g. by redirecting to a pipe, like popen does for one of them). It doesn't matter whether you use os.popen, subprocess.Popen, os.system, or os.fork to create the child process. So in your case if the parent inputs from the console, so does the child. But note: this is not communication from the parent process to the child, but from YOU to the child. So the parent-child communication is ONE WAY. >n> "... >>> doesn't work as the iterator for a file, including pipes, does a >>> read ahead (see the doc on file.next()) and therefore is not suitable >>> for interactive use. >n> ..." >n> If I understand you the above can be stated as: >n> The above does not work as an iterator for any file type, including >n> pipes, but it does do read aheads .... and therefore is not suitable for >n> interactive use. For files in general it is no problem because the contents of the file is not interactively generated. Read ahead on a file works as long as you do'nt use readline() on the file in between the iterator actions. For a socket it could be the same problem if the other side generates the output interactively. >n> If that is correct then read ahead is simply buffered file reads (grab a >n> chunk, parcel it out on demand) - yes? I don't know, I have looked into the source code but it isn't clear to me. I noticed that iteration didn't work and then looked up the documentation. It talks about read ahead for efficiency. >n> As for "... not suitable for interactive ..." Really? Except for >n> special purpose use the current interactive components are all buffered >n> for read ahead use. Check the actual code for your keyboard, your mouse >n> and so forth. It's the read ahead that allows faster time to completion. >n> It's why C-code has the putch function. Yes, but they only read what is available. The iterator apparently tries to read more and then has to wait. >n> Yes - Sync IS the bigger hammer! If that is what is needed - so be it. >n> All character readers (byte at a time) should obey a flush(). Depending >n> on type, code for the reader controls whether or not it flushes >n> incomplete "lines" in the in-buffer(s). Proper implementation limits lost >n> data on system crash. I don't understand what you say here. As I told before it has nothing to do with sync(). Also for reading there is no flush(); the flush() is done on the other side of the pipe. Yes, and sync() has to do with system crashes but that is not what we are talking about in this thread. >n> In trying to use flush at the master side I keep getting messages >n> indicating strings (completed or not) are not flushable. Strange practice. If you print to the console in the master the flush is done automatically. >n> --- >n> from subprocess import Popen, PIPE >n> xx = Popen(["z6.py"], stdout=PIPE).stdout >n> while True: >n> line = xx.readline() >n> if not line: break >n> print "\t" + line, >n> --- >n> DOES WORK on Python 2.5.2 on Slackware 10.2 - THANK YOU VERY MUCH!!! >n> Isn't working on Windows. error message comes as one of two forms. >n> 1- %1 not found #as shown above >n> 2- file not found #as ...["python z6.py"]... >n> same #as #2 even with full paths given That should be Popen(["python", "z6.py"], stdout=PIPE).stdout And then with both python and z6.py given as full paths. >n> I get the impression subprocess ignores system things on Windows. >n> The routines it purposes to replace do use them. At any rate, subprocess >n> is NOT consistent across platforms. subprocess is, but Windows isn't. On Unix-like systems, the python command is usually in your PATH, so just giving "python" works. In Windows PATH is underused, and commands like python often are not in PATH, unless you as a user has adapted the path, or maybe there is an installation option to adapt the PATH. The reason probably is that in Windows almost nobody uses the command line but only clicks and the PATH is not relevant. >n> Some questions: >n> 1) "...], stdout=PIPE).stdout >n> ^ ^ why the double use? It is not a double use. Popen(["z6.py"], stdout=PIPE) gives you a Popen object, not a file object. If you add .stdout you get the stdout attribute of the Popen object of which you just before stated that it should be a pipe. So the stdout=PIPE parameter makes it create a pipe, and the .stdout returns you that pipe. >n> 2) "if not line: break" what tells what to look for EOL >n> or is the use of 'line' missleading? >n> is it a byte at a time output? No, line is a line, as indicated by the readline() call. The "if not line" is a test for end of file. In this case the end of the child process (pipe closed). >n> how much CPU usage does the loop use? Not much, It is mainly waiting for input but that doesn't consume CPU. >n> is there something in that loop that >n> uses the system pipe triggers to >n> reduce excessive CPU waste or does it >n> constantly poll? If so where does >n> what code get put to signal (or set) >n> the courtesy semiphores so it does >n> not hog the system? It doesn't poll or use semaphores. The beauty of a pipe is that it automatically synchronises the reader and writer processes. If you do a read on a pipe and it is empty the OS just blocks you. When the other end writes something in the pipe, the OS will unblock you. -- Piet van Oostrum <piet(a)cs.uu.nl> URL: http://pietvanoostrum.com [PGP 8DAE142BE17999C4] Private email: piet(a)vanoostrum.org

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Simple metaclass code failing
by LittleGrasshopper June 1, 2009

June 1, 2009

This is some simple code which I got from Guido's paper on the unification of classes and types, which Arnaud suggested to improve my knowledge of metaclasses: class M1(type): pass class M2(M1): pass class M3(M2): pass class C1: __metaclass__ = M1 class C2(C1): __metaclass__ = M2 class C3(C1, C2): __metaclass__ = M3 It is failing when processing C3: Traceback (most recent call last): File "metaerror.py", line 18, in <module> class C3(C1, C2): TypeError: Error when calling the metaclass bases Cannot create a consistent method resolution order (MRO) for bases C2, C1 Since M3 is a subclass of M1 and M2 (which are the metaclasses for the bases of C3, I don't understand the error. Then again, the error seems to reference the MRO. I hope this is one of those posts that I can look back in a few months from now and think "Man, was that a dumb thing to ask!" Until then, I would appreciate your help in trying to figure out what's going on. Lukas

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screen scraping
by ubuntu.exe＠gmail.com June 1, 2009

June 1, 2009

Hello, does anybody have a simple tutorial for screen scrapping? I want to extract IP addresses from particular web page, reading documentation for a couple of days and writing some really simple scripts, but cant get it to work. Did anybody see any manual explicittly for screen scraping? Thanks.

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Re: What text editor is everyone using for Python
by Lie Ryan June 1, 2009

June 1, 2009

norseman wrote: > jeffFromOz wrote: >> On May 26, 10:07 pm, Lacrima <Lacrima.Ma...(a)gmail.com> wrote: >>> I am new to python. >>> And now I am using trial version of Wing IDE. >>> But nobody mentioned it as a favourite editor. >>> So should I buy it when trial is expired or there are better choices? >> >> No one mentioned textmate either . a brilliant text editor with >> python templates, and bundles, syntax highlighting, etc. We use >> wingIDE for debugging and it seems fine, except for the weird way it >> corrupts the displayed text. > =========================== > > BOTTOM LINES: > > Whatever they learned on. > Whatever they are trying out at the moment (for the adventurous types) > > > Suggestion: > Take a look at the top two most used OS you use and learn the default > (most often available) text editors that come with them. Which means Notepad on Windows?

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Ah, ctypes
by Lawrence D'Oliveiro June 1, 2009

June 1, 2009

I wrote some code months ago to output 1-bit-per-pixel PNG files from Python, doing direct calls to libpng using ctypes, because PIL didn't give me sufficient control over colour tables and pixel depths. I thought the code was working fine. I left it aside for some months, came back to it a week or two ago, and found it was crashing. I was creating CFUNCTYPE objects to do callbacks to my own I/O routines, and with GDB I was able to narrow down the crashes to the point where libpng was trying to invoke one of my callbacks. What had changed? I had switched my OS from Gentoo to Debian Unstable. I chrooted back to the Gentoo system, tried my script again--still crashed. Went back to the doc <http://docs.python.org/library/ctypes.html> and tried the qsort callback example. Worked fine! And then I noticed this little bit: Important note for callback functions: Make sure you keep references to CFUNCTYPE objects as long as they are used from C code. ctypes doesn’t, and if you don’t, they may be garbage collected, crashing your program when a callback is made. Yup, that was it. I changed my installation of the callbacks from png.png_set_write_fn \ ( write_struct, None, ct.CFUNCTYPE(None, ct.c_void_p, ct.c_void_p, ct.c_size_t)(write_data), ct.CFUNCTYPE(None, ct.c_void_p)(flush_write) ) to cb_write_data = ct.CFUNCTYPE(None, ct.c_void_p, ct.c_void_p, ct.c_size_t)(write_data) cb_flush_write = ct.CFUNCTYPE(None, ct.c_void_p)(flush_write) png.png_set_write_fn \ ( write_struct, None, cb_write_data, cb_flush_write ) and it works again.

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Urllib2 proxy settings
by K-Dawg June 1, 2009

June 1, 2009

Hello, I am having trouble with an application running on a linux server. It keeps reverting to old proxy settings and messing up the web application. I have checked everything I can think of, and since the application is written in Python and uses urllib to call a web service (which is where the error is occurring) I thought that I could open up the interpreter, import URLLib2 and then see what it thinks the proxy is. How can I just echo this in the interpreter? Thanks. Kevin

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Re: which database is suitable for small applications
by Ankit June 1, 2009

June 1, 2009

Hi Kalyan... If your application does not require you to add very heavy data then you can also use flat files to do your stuff. Its always a better to use Databases but given your low level use and newness to python... i would advise you to take up flat files instead. store your data there and access it.. simple! ANkit

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Parsing Data
by babypython June 1, 2009

June 1, 2009

I am trying to parse through this data for analysis. I am new to python and wondering what would be the quickest way to extract the data from this file. The data files consists of comments (starting with ! and #). Then, the data follows. All I want is the data in array ( I don't care about the comments),and the data format is freq[], s11[real], s11[imag], s21[real],s21[imag] Any help will be appreciated. Thanks. !Date: Jan 29, 2008 14:40:26 !Correction: S11(Full 2 Port(1,2)) S21(Full 2 Port(1,2)) !Measurements: S11, S21: ! Freq S11[real, imag] S21[real,imag] 1400000000 -2.104572e+001 4.153887e+001 -4.084314e+001 8.417739e+001 1400250000 -2.089971e+001 4.028599e+001 -4.087196e+001 7.026196e+001 1400500000 -2.114216e+001 4.086434e+001 -4.055134e+001 6.559201e+001 1400750000 -2.112057e+001 3.681709e+001 -4.024515e+001 5.503412e+001 1401000000 -2.110984e+001 3.622524e+001 -4.056519e+001 5.162795e+001 1401250000 -2.123562e+001 3.602308e+001 -4.125660e+001 4.330296e+001 1401500000 -2.152193e+001 3.345480e+001 -4.035107e+001 3.937940e+001 1401750000 -2.144410e+001 3.189340e+001 -4.097492e+001 2.802726e+001 1402000000 -2.155891e+001 3.002732e+001 -4.146297e+001 1.666007e+001 1402250000 -2.170474e+001 2.896428e+001 -4.146934e+001 1.514847e+001 1402500000 -2.185459e+001 2.863795e+001 -4.053018e+001 1.130192e+001 -- View this message in context: http://www.nabble.com/Parsing-Data-tp23820003p23820003.html Sent from the Python - python-list mailing list archive at Nabble.com.

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