🌐 Mailman 3 April 2006 - Python-list - python.org

Re: Generate a sequence of random numbers that sum up to 1?
by Paul Rubin April 29, 2006

April 29, 2006

Anthony Liu <antonyliu2002(a)yahoo.com> writes: > OK, I actually just want to "manually" create Hidden > Markov Models by randomly generating the initial state > probabilities PI, OK, this sounds like you actually want to divide the unit interval up into pieces of varying sizes. Example (untested): n = 10 # number of pieces desired # Take the unit interval [0,1] and sprinkle in n-1 random points s = sorted([0,1] + [random() for i in xrange(n-1)]) # now find the size of each sub-interval and make a list r = [(s[i+1] - s[i]) for i in xrange(n)] print sum(r) # should be 1.0 within rounding error

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Re: self modifying code
by Steven Bethard April 29, 2006

April 29, 2006

John J. Lee wrote: > Robin Becker <robin(a)NOSPAMreportlab.com> writes: > >> When young I was warned repeatedly by more knowledgeable folk that self >> modifying code was dangerous. >> >> Is the following idiom dangerous or unpythonic? >> >> def func(a): >> global func, data >> data = somethingcomplexandcostly() >> def func(a): >> return simple(data,a) >> return func(a) > > 1. I don't think most people would call that "self-modifying code". I > won't try defining that term precisely because I know you'll just > pick holes in my definition ;-) > > 2. The use of global func is just plain weird :-) > > 3. Peter Otten's version is OK, but how about this, using a closure > instead of globals (UNTESTED) > > def make_func(): > namespace = object() > namespace.data = None > def func(a): > if namespace.data is None: > namespace.data = somethingcomplexandcostly() > return simple(namespace.data, a) > return func > func = make_func() Unfortunately, this doesn't work because you can add attributes to plain object instances: >>> namespace = object() >>> namespace.data = None Traceback (most recent call last): File "<interactive input>", line 1, in ? AttributeError: 'object' object has no attribute 'data' Maybe you want something like: >>> def make_func(): ... def func(a): ... if func.data is None: ... func.data = somethingcomplexandcostly() ... return simple(func.data, a) ... func.data = None ... return func ... >>> func = make_func() >>> def somethingcomplexandcostly(): ... print 'executing somethingcomplexandcostly' ... return 42 ... >>> def simple(data, a): ... return data, a ... >>> func(1) executing somethingcomplexandcostly (42, 1) >>> func(2) (42, 2) STeVe

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Why does bufsize=1 not work in subprocess.Popen ?
by I. Myself April 29, 2006

April 29, 2006

I read in the docs that "bufsize=1" causes line buffering. (for subprocess.Popen) The following tiny program launches an executable file and then receives its output. That works, but I want to receive each line as it is ouput, not all of the lines at termination, which is what is happening. ------------------------------------------------------- from subprocess import Popen, PIPE from os import remove, sep p = Popen("." + sep + "myprogram", stdout=PIPE, bufsize=1) while(1): line = p.stdout.readline() # get next line print line, if line.count("terminator"): break ------------------------------------------------------ How can I get line buffering? Mitchell Timin -- I'm proud of http://ANNEvolve.sourceforge.net. If you want to write software, or articles, or do testing or research for ANNEvolve, let me know. Humans may know that my email address is: (but remove the 3 digit number) zenguy at shaw666 dot ca

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Re: Using Databases in Python
by Petr Jakes April 29, 2006

April 29, 2006

Thank you very much, Steve. Petr Jakes

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Re: (was Re: Xah's Edu Corner: Criticism vs Constructive Criticism)
by James Stroud April 29, 2006

April 29, 2006

bruce wrote: > but you know... > > one could simply hit the delete/skip button when you see a msg you don't > like!!! or email/spam filters... or you can spend more time complaining.. in > life, you gotta' learn to pick your battles... > > peace.. > Bruce: You may want to check your mail reader to make sure it responds to the thread. That would help people to "skip" messages. The thread in question got out of hand a long time ago (even before I jumped in ;), so it would help if related posts replied to the thread--at least thunderbird does not group your post with the thread. I'm guessing other news readers won't either. Also, there is no doubt that you will soon be chastised for "top posting": http://en.wikipedia.org/wiki/Top-posting James -- James Stroud UCLA-DOE Institute for Genomics and Proteomics Box 951570 Los Angeles, CA 90095 http://www.jamesstroud.com/

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Re: urllib.urlopen() with pages that requires cookies.
by mwt April 29, 2006

April 29, 2006

Fredrik Lundh wrote: > Øyvind Østlund wrote: > > > I am trying to visit a limited amount of web pages that requires cookies. I > > will get redirected if my application does not handle them. I am using > > urllib.urlopen() to visit the pages right now. And I need a push in the > > right direction to find out how to deal with pages that requires cookies. > > Anyone have any idea how to go about this? > > use urllib2 and cookielib. here's an outline: > > import urllib2, cookielib > > # set things up > jar = cookielib.CookieJar() > handler = urllib2.HTTPCookieProcessor(jar) > opener = urllib2.build_opener(handler) > urllib2.install_opener(opener) > > data = urllib2.urlopen(someurl).read() > > # ... > > data = urllib2.urlopen(someotherurl).read() > > # ... > > # dump cookie jar contents (for debugging) > for cookie in jar: > print cookie > > </F> How would this outline be changed/expanded if it also needed to handle basic authentication?

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Urllib2 / add_password method
by mrstephengross April 29, 2006

April 29, 2006

I'm working on learning how to use urllib2 to use a proxy server. I've looked through the postings on this group, and it's been helpful. I have not, however, found complete documentation on the add_password() functions. Here's what I've got so far: #======================================== import urllib2 url = 'http://some.server/form.php' proxy_url = 'http://202.62.252.3:8080' # A publicly available anonymous proxy server proxy_handler = urllib2.ProxyHandler( {'http': proxy_url } ) proxy_auth_handler = urllib2.HTTPBasicAuthHandler() proxy_auth_handler.add_password('realm', 'host', 'username', 'password') opener = urllib2.build_opener(proxy_handler, proxy_auth_handler) urllib2.install_opener(opener) try: handler = urllib2.urlopen(url) except urllib2.URLError: print "whoops!" else: print handler.read() #======================================= It works, but I don't really know what I'm doing with the proxy_auth_handler part. Specifying username and password make sense, but I haven't found documentation on what 'realm' and 'host' are for. Shouldn't username & password be sufficient? Thanks, --Steve (mrstephengross(a)hotmail.com)

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Re: A QFB agent: how to catch C-level crashes and last Python stack ?
by robert April 29, 2006

April 29, 2006

Thomas Heller wrote: > robert wrote: > >> When employing complex UI libs (wx, win32ui, ..) and other extension >> libs, nice "only Python stack traces" remain a myth. >> >> Currently I'm hunting again a rare C-level crash bug of a Python based >> Windows app with rare user reports - and still in the dark (I get >> snippets of machine stack traces / screenshots with random "mem. >> access error" / "python caused the runtime to terminate in an unusual >> way" / ..) >> >> I'd like to hook a kind of quality feedback agent a C-level to enable >> the user transfer a report (similar to what Mozilla/Netscape has), >> e.g. in a changed python.exe stub. Next to the machine stack/regs it >> should grab the relevant last Python thread stack(s), if any, and >> maybe other useful status and python global vars. >> (There are also Python threads going on. ) >> >> Is that possible? >> >> -robert > > > It looks like this may be what you want. Quoting from > > http://www.usenix.org/events/usenix01/full_papers/beazley/beazley.pdf > > """ > In recent years, scripting languages such as Perl, > Python, and Tcl have become popular development tools > for the creation of sophisticated application software. > One of the most useful features of these languages is > their ability to easily interact with compiled languages > such as C and C++. Although this mixed language approach > has many benefits, one of the greatest drawbacks > is the complexity of debugging that results from using > interpreted and compiled code in the same application. > In part, this is due to the fact that scripting language > interpreters are unable to recover from catastrophic errors > in compiled extension code. Moreover, traditional > C/C++ debuggers do not provide a satisfactory degree > of integration with interpreted languages. This paper > describes an experimental system in which fatal extension > errors such as segmentation faults, bus errors, and > failed assertions are handled as scripting language exceptions. > This system, which has been implemented as > a general purpose shared library, requires no modifications > to the target scripting language, introduces no performance > penalty, and simplifies the debugging of mixed > interpreted-compiled application software. > """ > > It may be an interesting project to port this to Windows. > > Hope that helps, > Thanks, exactly. That would be quite luxurious as WAD manages to even continue normal Python execution on the current stack (only in a UNIX main thread?) with a regular Python exception. That would make pets out of all bugs - preventing users from facing nameless app freezes, but make the help bug elimination for distributed programs by detailed reports. simply catching signal.SIGSEGV with Python's signal module causes just looping at 100% CPU load (The GIL is not forced ?) WAD obviously has not anymore evolved since the beginning. The Author says, that a Windows port would be quite complex - because advanced execution context manipulation is obviously not possible with signals on Windows. Yet he mentions the Windows C++ "structured exception handling", which may enable that. I know that the fast Object Store OO-Database uses exactly that method to catch and recover execution from seg faults, while updating a kind of memory mapped database into the system. I integrated that OO-DBMS exception handler once with Python some years back by making a C++ file out of python.c as shown below or even by using that PSECall alone, which is needed anyway for wrapping any other Python threads (start functions) with the seg fault handler. Probably there is even better thread control possible than on Linux. Yet I don't know so far if its possible to find the valid Python exit functions on the stack (for returning from exceptions) the same style as in Unix ELF binaries ... -- #define OS_PSE_ESTABLISH_FAULT_HANDLER \ { try { _PSE_NS_ _ODI_fault_handler _ODI_handler; try { .. #define OS_PSE_END_FAULT_HANDLER \ } catch (_PSE_NS_ os_err& e) { e.print(); } \ } catch (_PSE_NS_ _ODI_fault_handler&) {} } .. #include <os_pse/ostore.hh> #include "Python.h" extern "C" { DL_EXPORT(int) Py_Main(int, char**);} int main(int argc, char **argv) { int result=0; // The top of the stack of every thread of every program // must be wrapped in a fault handler // This macro begins the handler's scope OS_PSE_ESTABLISH_FAULT_HANDLER result = Py_Main(argc, argv); // This macro ends the fault handler's scope OS_PSE_END_FAULT_HANDLER return result; } --- #ifdef SWIG //# for wrapping python threads with the PSE fault handler %native(PSECall) _wrap_PSECall; %{ //#include <os_pse/ostore.hh> //#include "Python.h" static PyObject *_wrap_PSECall(PyObject *self, PyObject *args) { PyObject * func =0 ; PyObject * funcargs =0 ; PyObject* result; if(!PyArg_ParseTuple(args,"OO:PSECall",&func, &funcargs)) return NULL; // The top of the stack of every thread of every program // must be wrapped in a fault handler // This macro begins the handler's scope OS_PSE_ESTABLISH_FAULT_HANDLER result = PyEval_CallObject(func,funcargs); // Call Python // This macro ends the fault handler's scope OS_PSE_END_FAULT_HANDLER return result; } %} #endif // SWIG --- -robert

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Re: self modifying code
by Robin Becker April 29, 2006

April 29, 2006

John J. Lee wrote: > 1. I don't think most people would call that "self-modifying code". I > won't try defining that term precisely because I know you'll just > pick holes in my definition ;-) Don't really disagree about the rewriting code, but the function does re-define itself. > 2. The use of global func is just plain weird :-) > > 3. Peter Otten's version is OK, but how about this, using a closure > instead of globals (UNTESTED) > > def make_func(): > namespace = object() > namespace.data = None > def func(a): > if namespace.data is None: > namespace.data = somethingcomplexandcostly() > return simple(namespace.data, a) > return func > func = make_func() > ....... the inner function is almost precisely what I started with, except I used the global namespace. However, it keeps the test in side the function which costs about 1%. -- Robin Becker

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opposite function to split?
by randomtalk＠gmail.com April 29, 2006

April 29, 2006

hello everyone! I can't seem to find a function that combines a list of items into a string with a seperator between the individual elements.. Is there such a method that does the opposite of sting.split? thanks alot!

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