🌐 Mailman 3 October 2008 - Python-list - python.org

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by chinu Oct. 30, 2008

Oct. 30, 2008

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math equation, svg and matplotlib
by André Oct. 30, 2008

Oct. 30, 2008

Would anyone have a "quick and dirty" code sample to create an svg output of a sample math equation using matplotlib? André

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guenstige kredite
by coolkid246＠googlemail.com Oct. 30, 2008

Oct. 30, 2008

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Re: Filter function and lists
by Mensanator Oct. 30, 2008

Oct. 30, 2008

On Oct 29, 4:28 pm, Terry Reedy <tjre...(a)udel.edu> wrote: > John Townsend wrote: > > I’m trying to figure out how to use filter to walk through a list. > > > If I try a simple scripts like this: > > > def greaterthanten (number): > > #pdb.set_trace() > > if (number > 10): > > ret_val = 1 > > > else: > > ret_val = 0 > > > return ret_val > > > old_list = [1,2,20,30,5] > > > new_list = filter(greaterthanten, old_list) > > > #new_list becomes [20, 30] > > > The script works as I would expect. However, what if I need to pass more > > than one argument to the function? Can I do that with filter? Or does > > filter work only with function that take only a single arg? That single argument could be a list. >>> old_list = [1,2,20,30,5] >>> def power_of_10(a): if a[0]%10==0 and a[0]<a[1]: return True else: return False >>> new_list = [i[0] for i in filter(power_of_10,[[i,the_limit] for i in old_list])] >>> new_list [20, 30] >>> the_limit = 25 >>> new_list = [i[0] for i in filter(power_of_10,[[i,the_limit] for i in old_list])] >>> new_list [20] > > The latter. Other functions could be wrapped to bind all parameters > except the list element. Or write an explicit loop.- Hide quoted text - > > - Show quoted text -

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Re: Why gives "k = 09" a syntax error ?
by Mensanator Oct. 29, 2008

Oct. 29, 2008

On Oct 29, 4:25 pm, Terry Reedy <tjre...(a)udel.edu> wrote: > Stef Mientki wrote: > > hello, > > > Why gives "k = 09" a syntax error ? > > You have gotten the 2.x answer. In 3.0, 0b,0o,0x prefixes are valid and > required for binary, octal, and hexadecimal literals. 0digits is invalid. > > tjr Is it documented? :-)

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Re: how to get the thighest bit position in big integers?
by Mensanator Oct. 29, 2008

Oct. 29, 2008

On Oct 29, 4:16 pm, Glenn Linderman <v+pyt...(a)g.nevcal.com> wrote: > On approximately 10/29/2008 11:51 AM, came the following characters from > the keyboard of Mensanator: > > > or in 2.6 > > > print 'highest bit position: %d' % (len(bin(3328)[2:])-1) > > > highest bit position: 11 > > This works, but where is it documented? Good question. Now that I think about it, I believe I learned of it here, never saw it in the docs. > Searching the Python 2.6 docs > for bin found lots of things that start with bin, but none of them were > bin. Searching the builtins page manual didn't find it. Is this a bug > in the documentation? Well ,it's mentioned in "What's new in Python 2.6": <quote> Python 3.0 adds several new built-in functions and change the semantics of some existing built-ins. Entirely new functions such as bin() have simply been added to Python 2.6, but existing built-ins haven’t been changed; </quote> You would think when you add a new function, you would also add it's documentation, but maybe that was an oversight. I don't have 3.0, but maybe it can be found in that set of docs. > > -- > Glenn --http://nevcal.com/ > =========================== > A protocol is complete when there is nothing left to remove. > -- Stuart Cheshire, Apple Computer, regarding Zero Configuration Networking

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Re: Finding the instance reference of an object
by Dale Roberts Oct. 29, 2008

Oct. 29, 2008

On Oct 28, 11:59 am, Joe Strout <j...(a)strout.net> wrote: > ... > > There are only the two cases, which Greg quite succinctly and > accurately described above. One is by value, the other is by > reference. Python quite clearly uses by value. Parameters are > expressions that are evaluated, and the resulting value copied into > the formal parameter, pure and simple. The continued attempts to > obfuscate this is pointless and wrong. > > Best, > - Joe Joe, you are being too generous and expansive here. [Play along with me for a minute here...] Don't you know? There is really only *ONE* case, and, you are right, it is Pass By Value. There is no such thing as Pass By Reference at the physical CPU level at all, right? If there is, show it to me. Pass By Reference is just a silly idiom developed by high-minded CS academics to confuse the rest of us. It has no practical use and should not be given its own name, when we already have a good an proper name for it. Let me demonstrate with 3 examples of a function definition, and the appropriate calling syntax for that function in C++, all sharing the common "int i" global variable: int i = 5; myfunc(int &val){} /*CALL:*/ myfunc(i); // "ByRef" (ya, right!) myfunc(int val){} /*CALL:*/ myfunc(i); // ByVal myfunc(int *val){} /*CALL:*/ myfunc(&i); // Joe's ByVal The first is what all the fakers call "Pass By Reference" - sheesh, how naive. We all know that what *really* happens internally is that the *address* of val (A VALUE itself, or course) is copied and passed on the stack, right? There couldn't be a more straightforward example of Pass By Value (unless it's an inline function, or optimized away, or possibly when implemented in a VM, or...). It passes the *address* of i by value, then we can access the *value* of i too via indirection. Hmm, did we need to have two definitions of VALUE there? Well, never mind, no one will notice... The next is obviously pass by value. It's right out there. The value of i (which is what we are talking about, right?) is copied out, and passed right on the stack in plain daylight where we can all see it. How about the third? Pass By Value, obviously, of course. This is the version you are defending, right? The parameter's value, &i, is evaluated and copied right onto the stack, just like in the first example. In fact, if you compare the assembler output of the first and third examples, you may not even see a difference. Never mind the actual contents of that pesky "i" variable that most people are referring to when they use the term "value". We don't need to dress up example 3 and call it an "idiom" where we are really passing a so- called "reference" of the variable "i". Indeed! Don't insult our intelligence. We can all see that it's an address passed by value, plain and simple. Pass By Reference? So "postmodern". Who needs it. Show me a so-called "reference". I've looked at the assembler output and have never seen one. There is no such thing. "The continued attempts to obfuscate this is pointless and wrong." --------------- I hate to have to add this, but for those not paying close attention: ;-) dale (tongue back out of cheek now)

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Re: 2.6, 3.0, and truly independent intepreters
by Andy O'Meara Oct. 29, 2008

Oct. 29, 2008

> Are you familiar with the API at all? Multiprocessing was designed to > mimic threading in about every way possible, the only restriction on > shared data is that it must be serializable, but event then you can > override or customize the behavior. > > Also, inter process communication is done via pipes. It can also be > done with messages if you want to tweak the manager(s). > I apologize in advance if I don't understand something correctly, but as I understand them, everything has to be serialized in order to go through IPC. So when you're talking about thousands of objects, buffers, and/or large OS opaque objects (e.g. memory-resident video and images), that seems like a pretty rough hit of run-time resources. Please don't misunderstand my comments to suggest that multiprocessing isn't great stuff. On the contrary, it's very impressive and it singlehandedly catapults python *way* closer to efficient CPU bound processing than it ever was before. All I mean to say is that in the case where using a shared address space with a worker pthread per spare core to do CPU bound work, it's a really big win not to have to serialize stuff. And in the case of hundreds of megs of data and/or thousands of data structure instances, it's a deal breaker to serialize and unserialize everything just so that it can be sent though IPC. It's a deal breaker for most performance-centric apps because of the unnecessary runtime resource hit and because now all those data structures being passed around have to have accompanying serialization code written (and maintained) for them. That's actually what I meant when I made the comment that a high level sync object in a shared address space is "better" then sending it all through IPC (when the data sets are wild and crazy). From a C/C++ point of view, I would venture to say that it's always a huge win to just stick those "embarrassingly easy" parallelization cases into the thread with a sync object than forking and using IPC and having to write all the serialization code. And in the case of huge data types-- such as video or image rendering--it makes me nervous to think of serializing it all just so it can go through IPC when it could just be passed using a pointer change and a single sync object. So, if I'm missing something and there's a way so pass data structures without serialization, then I'd definitely like to learn more (sorry in advance if I missed something there). When I took a look at multiprocessing my concerns where: - serialization (discussed above) - maturity (are we ready to bet the farm that mp is going to work properly on the platforms we need it to?) Again, I'm psyched that multiprocessing appeared in 2.6 and it's a huge huge step in getting everyone to unlock the power of python! But, then some of the tidbits described above are additional data points for you and others to chew on. I can tell you they're pretty important points for any performance-centric software provider (us, game developers--from EA to Ambrosia, and A/V production app developers like Patrick). Andy

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Re: How to Implement an XMLRPC Server in Python?
by Diez B. Roggisch Oct. 29, 2008

Oct. 29, 2008

Guilherme Polo schrieb: > On 10/29/08, Zix <saviourms(a)yahoo.co.in> wrote: >> Hello, >> I am a newbie to python and trying to get a hang of some of its >> advanced features through an application I am building. Basically, I'd >> like to build a weather forecasting web service. The clients should be >> able to query the service with a location and date and get back the >> weather forecast. >> >> After reading a lot on the topic I've settled on the following: >> * not using any python frameworks (Django, pylons etc) >> * exposing the service through an XMLRPC API using Python 2.4.3 >> (that's the python version on CentOS 5.2) > > Why did you decide to "expose" a web service through xmlrpc instead of > actually exposing it by using a restful web service ? > > The links pointed by the previous email should help you, but well, I'm > still surprised on this decision specially because you said you read a > lot about this topic. What is wrong with XMLRPC? I've implemented both kind of systems, and while REST has it's strengths in a HTML-centric environment, a real RCP mechanism with built-in type marshalling known to both sides of the communication is for pure interoperability better. Diez

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project in python
by asit Oct. 29, 2008

Oct. 29, 2008

I am a newbie and learned python to some extent. I want to do some project in python based on network programming or HTML/XML parsing. Can anyone suggest me about this ???

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