Release of PyGreSQL 4.0 (update)
Update: The Windows binaries are now available on the web site. We are please to announce the release of PyGreSQL 4.0. his is a major release and you should check it carefully before using in existing applications. There may be some incompatibilities. PyGreSQL is a Python module that interfaces to a PostgreSQL database. It embeds the PostgreSQL query library to allow easy use of the powerful PostgreSQL features from a Python script. For more information, please visit http://www.PyGreSQL.org/. From the changelog: - Dropped support for Python below 2.3 and PostgreSQL below 7.4. - Improved performance of fetchall() for large result sets by speeding up the type casts (as suggested by Peter Schuller). - Exposed exceptions as attributes of the connection object. - Exposed connection as attribute of the cursor object. - Cursors now support the iteration protocol. - Added new method to get parameter settings. - Added customizable row_factory as suggested by Simon Pamies. - Separated between mandatory and additional type objects. - Added keyword args to insert, update and delete methods. - Added exception handling for direct copy. - Release the GIL while making a connection (as suggested by Peter Schuller). - If available, use decimal.Decimal for numeric types. - Allow DB wrapper to be used with DB-API 2 connections (as suggested by Chris Hilton). - Made private attributes of DB wrapper accessible. - Dropped dependence on mx.DateTime module. - Support for PQescapeStringConn() and PQescapeByteaConn(); these are now also used by the internal _quote() functions. - Added 'int8' to INTEGER types. New SMALLINT type. - Added a way to find the number of rows affected by a query() with the classic pg module by returning it as a string. For single inserts, query() still returns the oid as an integer. The pgdb module already provides the rowcount cursor attribute for the same purpose. - Improved getnotify() by calling PQconsumeInput() instead of submitting an empty command. - Removed compatibility code for old OID munging style. - The insert() and update() methods now use the returning clause if possible to get all changed values, and they also check in advance whether a subsequent select is possible, so that ongoing transactions won't break if there is no select privilege. - Added protocol_version and server_version attributes. - Revived the user attribute. - The pg module now works correctly with composite primary keys; these are represented as frozensets. - Removed the undocumented and actually unnecessary view parameter from the get() method. - get() raises a nicer ProgrammingError instead of a KeyError if no primary key was found. - delete() now also works based on the primary key if no oid available and returns whether the row existed or not. -- D'Arcy J.M. Cain PyGreSQL Development Group http://www.PyGreSQL.org -- http://mail.python.org/mailman/listinfo/python-announce-list Support the Python Software Foundation: http://www.python.org/psf/donations.html
Re: Is there a better algorithm?
bearophile wrote: Fuzzyman: for i in l: u = None if len(i) == 2: k, v = i else: k, u, v = i That's the best solution I have seen in this thread so far (but I suggest to improve indents and use better variable names). In programming it's generally better to follow the KISS principle. Strange that nobody has suggested: for Tup in Lst: for item in Tup: print item, print Because if I recall correctly, all the OP was doing was printing the stuff. Gets a bit hairier if you want to return the values though. - if you replace the first print statement above with a yield and delete the second, bare print, you lose knowledge of which tuple the item belongs to. It is not trivial to do if you don't have a priori knowledge of the maximum and minimum tuple length. Seems to me it is one of those gems that is a PITA to do completely generally - basically because you don't know when you call it how many items to unpack - so you have to return a count or something, or just fall back on a two step approach - get the tuple from the list, then do something with the items in the tuple. - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
patch
Týká se to Pythonu okrajově, přesto to dávám sem. Myslím, že by se mohlo hodit i ostatním, kdo chtějí zkoušet pod Windows nové věci z development verze: Jak opatchovat (pythonýrský) soubor pod Windows? Co jsem udělal: 1/ stáhl jsem http://gnuwin32.sourceforge.net/packages/patch.htm 2/ nainstaloval pod amin, přidal cestu do ..bin .. do PATH 3/ stáhl http://bugs.python.org/file12561/conv.diff a uložil do Lib/idlelib 4/ cmd: patch conf.diff hází chybu: C:\prg\Python30\Lib\idlelibpatch conv.diff patching file IOBinding.py Assertion failed: hunk, file ../patch-2.5.9-src/patch.c, line 354 This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. Patchuje někdo tady pod Windows? Díky -- geon Pavel Kosina -- http://mail.python.org/mailman/listinfo/python-list
ACL in python
Hello, does anybody know about an ACL implementation for python, which is not tied to the filesystem? I would like to use ACL on different objects not on files, so the POSIX file access solution is not the one I am looking for. I would like to be able to define ACOs, AROs, but it would be even nicer, if there would be AXO possibility as well. I have tried to find already, but I wasn't really successful. John -- http://mail.python.org/mailman/listinfo/python-list
Re: Why not Ruby?
On Fri, 02 Jan 2009 09:00:01 -0800, r wrote: On Jan 2, 6:45 am, Steven D'Aprano st...@remove-this- cybersource.com.au wrote: On Thu, 01 Jan 2009 17:38:02 -0800, r wrote: He was not cross posting. You don't actually know what cross-posting is, do you? You've just earned a plonking for the next month. Do try to have at least half a clue by February. Steven i got you NOW! Everybody go and look at this thread, there Mr. Makinzie butts in and posts an off-topic question, and Steven answers it, contributing to the off-topicalitly of the thread. And has yet to apologize for it, or admit his screwup, but will he preach to everyone else about making off topic post... Pot meet Kettle; Kettle Pot! http://groups.google.com/group/comp.lang.python/browse_thread/thread/ fc57c18c3cff5937?hl=enq=recycle+bin#97254d877903bbd No you didn't got Steven, as unnecessary cross posting is something different than answering a question that should have been a new thread start. Oh, and: *plonk* for your childish annoying behaviour… Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: why cannot assign to function call
On Fri, 02 Jan 2009 04:39:15 -0600, Derek Martin wrote: On Tue, Dec 30, 2008 at 02:21:29PM +, John O'Hagan wrote: What the Python community often overlooks, when this discussion again rears its ugly head (as it seems to every other hour or so), is that its assignment model is BIZARRE, as in it's conceptually different from virtually all other languages substantially taught in undergraduate computer science programs. What's the difference between Python and Java or C# here!? Or are they also BIZARRE!? And for that matter, it's pretty unintuitive generally. Names and objects are quite natural IMHO. There are many real world objects which we attach one or more names to, or refer to in sequences like please give me the third book on that shelve (``shelve[2]``). That is, in what I'll call normal computer languages, a variable name is thought of as the address of a bin where some data is stored, and the name is inexorably tied to that bin. You just call that normal or intuitive because that's what you learned first. Python is very different from this. Names are not addresses of bins; they are instead simply ephemeral labels which are given to bins, where the bin is a Python object which contains specific data at the time of assignment. A second assignment of that name doesn't change what's in the original bin; it actually (probably) first creates a new bin, then removes the name from the original bin and assigns it to the new one. Intuitively, it's a bit like saying your kitchen table is no longer a kitchen table, and now the thing where you wash your dishes is a kitchen table. It doesn't really make a lot of sense (whether or not it's so for good reason), and it makes describing the assignment model necessarily convoluted, whereas the named bins model from the majority of other languages people are likely to have been exposed to is simple and sensible. I think the bin model is more complex because you don't just have a name and an object but always that indirection of the bin. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Ideas to optimize this getitem/eval call?
On Jan 3, 7:16 am, Steven D'Aprano st...@remove-this- cybersource.com.au wrote: I was about to make a comment about this being a security hole, Strange that you say this, as you are also implying that *all* the widely-used templating systems for python are security holes... Well, you would be right to say that of course ;-) Infact, evoque is really one of the few (or even the only one?) that was conceived from the start to support restricted evaluation. but I see from here http://evoque.gizmojo.org/usage/restricted/ that you are aware of at least some of the issues. I must say though, your choice of builtins to prohibit seems rather arbitrary. What is dangerous about (e.g.) id() and isinstance()? Preventive, probably. I also feel that temlates should have any business with info such as the memory addressed returnred by id(). For isinstance, becuase it is somewhat related to __subclasses__ that is known to be insecure. Incidentally, I updated the page you point to clarify what is going on. I also added a link to Brett Cannon's inspiration paper on the topic of securing the python interpreter... except: # KeyError, NameError, AttributeError, SyntaxError, # ValueError, TypeError, IOError If you want to capture seven exceptions, then capture seven exceptions, not any exception. Absolutely not. I want to catch ALL evaluation exceptions... it would actually *be* a secuity hole to allow any exception to bubble. hey will however be handled appropriately as per the application policy/ config/deployment. You should write: except (KeyError, NameError, ..., IOError): instead of a bare except clause. That will capture exceptions that represent bugs in your code as well as exceptions that should propbably be allowed to propagate, such as KeyboardInterupt and SystemExit. Again, no. Template presentational logic has no business issuing SystemExits or so. And, of course, there are no bugs in my code ;-) # Special case if a KeyError is coming from the self.codes[name] # lookup (traceback should consist of a single frame only): if sys.exc_info()[2].tb_next is None: if sys.exc_info()[0] is KeyError: self.codes[expr] = compile(expr, 'string', 'eval') return self[expr] That seems awfully complicated for no good reason. Yes, you are probably right. I wanted to be precise in that if the KeyError originates strictly from the codes lookup and not from the actual eval of the expr itself -- in which case the expr should be compiled and added to codes (yes, this is the first-time failure I referred to in the first message). I tested the performance of your 2 variations in context, and there seems to be no noticeable performance gain (something like less than 1% gain). But note the two variations as you code them do not quite do exactly the same test. I have adjusted to use this code now: def __getitem__(self, expr): try: return eval(self.codes[expr], self.globals, self.locals) except: # We want to catch **all** evaluation errors! # KeyError, NameError, AttributeError, SyntaxError, V # alueError, TypeError, IOError, ... # # Special case: # if KeyError is coming from self.codes[expr] lookup, # then we add the compiledentry and try again: if not name in self.codes: self.codes[expr] = compile(name, 'string', 'eval') return self[expr] # handle any other error... This retains the correctness of the check, and has the same marginal perf improvement (that is basically negligible, but at least it is not slower) and has teh advantage that the code is clearer. Thanks for the remarks! mario -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: ACL in python
John Boloshevich wrote: Hello, does anybody know about an ACL implementation for python, which is not tied to the filesystem? I would like to use ACL on different objects not on files, so the POSIX file access solution is not the one I am looking for. You mean something like the restricted environment you find within zope for all the TTW-stuff? Regards Tino smime.p7s Description: S/MIME Cryptographic Signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Ideas to optimize this getitem/eval call?
correction: the code posted in previous message should have been: def __getitem__(self, expr): try: return eval(self.codes[expr], self.globals, self.locals) except: # We want to catch **all** evaluation errors! # KeyError, NameError, AttributeError, SyntaxError, V # alueError, TypeError, IOError, ... # # Special case: # if KeyError is coming from self.codes[expr] lookup, # then we add the compiledentry and try again: if not expr in self.codes: self.codes[expr] = compile(expr, 'string', 'eval') return self[expr] # handle any other error... -- http://mail.python.org/mailman/listinfo/python-list
Re: multiprocessing vs thread performance
mk mrk...@gmail.com wrote: After reading http://www.python.org/dev/peps/pep-0371/ I was under impression that performance of multiprocessing package is similar to that of thread / threading. However, to familiarize myself with both packages I wrote my own test of spawning and returning 100,000 empty threads or processes (while maintaining at most 100 processes / threads active at any one time), respectively. The results I got are very different from the benchmark quoted in PEP 371. On twin Xeon machine the threaded version executed in 5.54 secs, while multiprocessing version took over 222 secs to complete! Am I doing smth wrong in code below? Yes! The problem with your code is that you never start more than one process at once in the multiprocessing example. Just check ps when it is running and you will see. My conjecture is that this is due to the way fork() works under unix. I think that when the parent forks it yields the CPU to the child. Because you are giving the child effectively no work to do it returns immediately, re-awakening the parent, thus serialising your jobs. If you give the children some work to do you'll see a quite different result. I gave each child time.sleep(1) to do and cut down the total number to 10,000. $ ./test_multiprocessing.py == Process 1000 working == == Process 2000 working == == Process 3000 working == == Process 4000 working == == Process 5000 working == == Process 6000 working == == Process 7000 working == == Process 8000 working == == Process 9000 working == == Process 1 working == === Main thread waiting for all processes to finish === Total time: 101.382129192 $ ./test_threading.py == Thread 1000 working == == Thread 2000 working == == Thread 3000 working == == Thread 4000 working == == Thread 5000 working == == Thread 6000 working == == Thread 7000 working == == Thread 8000 working == == Thread 9000 working == == Thread 1 working == Total time: 100.659118176 So almost identical results and as expected - we ran 10,000 sleep(1)s in 100 seconds so we must have been running 100 simultaneously. If you replace the time.sleep(1) with for _ in xrange(100): pass you get this much more interesting answer on my dual core linux laptop, showing nicely the effect of the contention on the python global interpreter lock and how multiprocessing avoids it. $ ./test_multiprocessing.py == Process 1000 working == == Process 2000 working == == Process 3000 working == == Process 4000 working == == Process 5000 working == == Process 6000 working == == Process 7000 working == == Process 8000 working == == Process 9000 working == == Process 1 working == === Main thread waiting for all processes to finish === Total time: 266.808327913 $ ./test_threading.py == Thread 1000 working == == Thread 2000 working == == Thread 3000 working == == Thread 4000 working == == Thread 5000 working == == Thread 6000 working == == Thread 7000 working == == Thread 8000 working == == Thread 9000 working == == Thread 1 working == Total time: 834.81882 -- Nick Craig-Wood n...@craig-wood.com -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list
Re: greenlets and how they can be used
James Mills prolo...@shortcircuit.net.au wrote: The greenlet from http://codespeak.net/py/dist/greenlet.html is a rather interesting way of handling flow of control. Ahh, yes. It's actually a rather old idea, but too rarely used. What can greenlet's be used for ? What use-cases have you guys used them for (if any) ? I've one project in which I use coroutines (either greenlets or some coroutines I concocted out of Python's built-in threading) extensively. The system consists of a server which speaks a text-based protocol (written in C), a graphical monitor program, and a number of ancillary services which are both clients of the server, and augment it by providing additional commands. The monitor and the services are all in Python, and make extensive use of coroutines. One reason for this is that some of the server's commands can take a long time, so it's useful for the programs to be able to do other things while they wait for replies. Full-on threading would be possible, but (a) in fact I make a /lot/ of coroutines, and (b) with coroutines I don't have to think anywhere near as hard about synchronization. You can browse about here, if you like: http://git.distorted.org.uk/gitweb/~mdw/tripe?a=tree;h=python The main Python module is in py/; the services are in svc/, and the graphical monitor is in mon/. Can they be used in place of threads with much the same effect - but more lightweight ? More lightweight, and much easier to reason about. They also confuse other libraries less. -- [mdw] -- http://mail.python.org/mailman/listinfo/python-list
Re: why cannot assign to function call
Derek Martin a écrit : On Fri, Jan 02, 2009 at 09:05:51PM +0100, Bruno Desthuilliers wrote: Python seems rather weird, and I think from the frequency with which these discussions occur on this list, clearly it *IS* difficult for a neophyte Python programmer to understand the assignment model. Took me about half an hour to grasp, not even being CS grad (nor whathever grad FWIW). By that time, I had a couple monthes working experience with VB, and had learned (but never seriously used) bits of C, C++, Java and Pascal. It took me about a half a second to grasp the named bins concept -- Oh yes ? With all it's implications ? Fine, you're way smarter than I'm - or, as it seems, you were much more experimented and CS-litterate that I was by that time. But that was not the point. What I meant is that a concept that takes less than an hour to grasp for a newbie self-taught programmer with no previous exposure to the concept should by no mean be a problem for a CS graduate. -- http://mail.python.org/mailman/listinfo/python-list
Re: Noob question: Is all this typecasting normal?
sprad a écrit : I've done a good bit of Perl, but I'm new to Python. I find myself doing a lot of typecasting (or whatever this thing I'm about to show you is called), Actually, it's just plain object instanciation. and I'm wondering if it's normal, or if I'm missing an important idiom. For example: bet = raw_input(Enter your bet) if int(bet) == 0: # respond to a zero bet raw_input() returns a string. If you want an int and the string is supposed to contain a legitimate string representation of an integer, then yes, passing the string to the int object constructor is the right thing to do. I'd just write it a bit diffently: bet = int(raw_input(Enter your bet)) if bet == 0: # code here or even better: def read_int(prompt, err=Sorry, '%s' is not a valid integer): while True: answer = raw_input(prompt) try: return int(answer) except ValueError: print err % answer bet = read_int(Enter your bet) if bet == 0: # code here Or later, I'll have an integer, and I end up doing something like this: print You still have $ + str(money) + remaining May suggest learning about string formatting ? print You still have $%s remaining % money But indeed, you obviously cannot add strings with numerics nor concatenate numerics with strings. This would make no sense. All the time, I'm going int(this) and str(that). Am I supposed to? Depends on the context. -- http://mail.python.org/mailman/listinfo/python-list
Doubt on creating threads
I was going through Python posts and this post caught my attention http://groups.google.com/group/comp.lang.python/browse_thread/thread/f99326a4e5d394e/14cd708956bd1c1a#14cd708956bd1c1a quote You have missed an important point. A well designed application does neither create so many threads nor processes. The creation of a thread or forking of a process is an expensive operation. You should use a pool of threads or processes. /unquote I am creating an application and it creates ~1-2 threads every second and kill it within 10 seconds. After reading this I am worried. Is creating a thread a very costly operation? I cannot use a pool of threads because I am using an external application (twisted) to create the threads (deferToThread). -- http://mail.python.org/mailman/listinfo/python-list
Re: why cannot assign to function call
On Tue, 30th Dec 2008, Aaron Brady wrote:
Accepting that, I'll adopt the terms John proposed, 'change' vs.
'exchange', the former when the material configuration changes, the
latter when the communication axioms change.
b= [2, 3]
b= [3, 4]
'b' has exchanged. (Somewhat ungrammatical.)
b= [2, 3]
b.append( 4 )
'b' has changed.
According to this, when you replace every floorboard on a porch, one
at a time, it's still the same porch-- it's changed, it's different,
and it's the same. However, if you haul off the porch and put a new
one in its place, it's not. ('porch[:]=' vs. 'porch='.) You can't
just look at the initial and final configurations of matter to
determine so. Therefore, 'id' is an informal function.
This analogy describes the ontological minefield I was referring to in a
previous post in this thread (which has expired in my mail reader, so my
apologies if the threading goes awry): In what sense is a porch (or list, or
string) the same if all (or even some of) its parts have been exchanged?
I think the answer is something to do with the abstraction, the container,
the instance of the class. Would it be fair to say that perhaps there are no
truly mutable objects, only immutable containers whose contents (also
immutable objects themselves) may be exchanged? Or to pose the question
another way, are objects only mutable insofar as they are composite?
As you argue above, the planks are not the porch; I would add that it's your
_decision_ to build (or tear down) a porch which makes it _that_ particular
porch (or not).
As you imply above (I think), you have to keep looking (or someone does,
presumably the interpreter) to know whether an object is the same as or just
equal to another (which starts to sound spookily like the role of the
observer in phenomenology or quantum physics). Whether this means that id()
is informal or not, I'll leave to others better informed than I.
Regards,
John
--
http://mail.python.org/mailman/listinfo/python-list
Re: select.select and socket.setblocking
Laszlo Nagy wrote: [...] I have read the socket programming howto ( http://docs.python.org/howto/sockets.html#sockets ) but it does not explain how a blocking socket + select is different from a non blocking socket + select. Is there any difference? There is, but it may not effect you. There are cases where a socket can select() as readable, but not be readable by the time of a following recv() or accept() call. All such cases with which I'm familiar call for a non-blocking socket. Where does this come up? Suppose that to take advantage of multi-core processors, our server runs as four processes, each with a single thread that responds to events via select(). Clients all connect to the same server port, so the socket listening on that port is shared by all four processes. A perfectly reasonable architecture (though with many more processes the simple implementation suffers the thundering herd problem). Two of our processors may be waiting on select() when a new connections comes in. The select() call returns in both processes, showing the socket ready for read, so both call accept() to complete the connection. The O.S. ensures that accept() [and recv()] are atomic, so one process gets the new connection; what happens in the other depends on whether we use a blocking or non-blocking socket, and clearly we want non-blocking. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: why cannot assign to function call
On 2009-01-03, Marc 'BlackJack' Rintsch bj_...@gmx.net wrote: On Fri, 02 Jan 2009 04:39:15 -0600, Derek Martin wrote: What the Python community often overlooks, when this discussion again rears its ugly head (as it seems to every other hour or so), is that its assignment model is BIZARRE, as in it's conceptually different from virtually all other languages substantially taught in undergraduate computer science programs. What's the difference between Python and Java or C# here!? Or scheme, or lisp, or smalltalk, or Or are they also BIZARRE!? One presumes that Mr. Martin finds anything different from his first computer language to be BIZARRE. He should try out Prolog or something genuinely different. -- Grant -- http://mail.python.org/mailman/listinfo/python-list
strange thing after call PyObject_CallMethod
Hello everybody! I'm in trouble. This code shows that ob_refcnt increased by python if on_recv method throws exception. This occurs only if base C-class subclassed in python code. == my_old_refcnt = Py_REFCNT(self); py_result = PyObject_CallMethod(self, on_recv, (y#), recvbuf, result); my_new_refcnt = Py_REFCNT(self); log_debug(refcnt before call %d, my_old_refcnt); log_debug(after call: %d\n, my_new_refcnt); == Output: == tcpconn.c: refcnt before call 1 tcpconn.c: after call: 2 == If PyObject_CallMethod returns success(any non-NULL value) anything okay. Tested on Python 3.1a0 (py3k:68145M, Jan 2 2009, 20:51:28). Why this happenning and who makes Py_INCREF(self)? PS garbage collector knows about this so on exit PyGC_Collect deletes instance. -- //wbr Kandalintsev Alexandre -- http://mail.python.org/mailman/listinfo/python-list
Re: Doubt on creating threads
On Sat, 3 Jan 2009 08:39:52 -0800 (PST), koranth...@gmail.com wrote: I was going through Python posts and this post caught my attention http://groups.google.com/group/comp.lang.python/browse_thread/thread/f99326a4e5d394e/14cd708956bd1c1a#14cd708956bd1c1a quote You have missed an important point. A well designed application does neither create so many threads nor processes. The creation of a thread or forking of a process is an expensive operation. You should use a pool of threads or processes. /unquote I am creating an application and it creates ~1-2 threads every second and kill it within 10 seconds. After reading this I am worried. Is creating a thread a very costly operation? I cannot use a pool of threads because I am using an external application (twisted) to create the threads (deferToThread). Actually, deferToThread is implemented in terms of a thread pool. So you're only creating a small number of threads, and then they're being re-used. I somewhat disagree with the assertion that not using a threadpool means that your application is well designed. However, it's absolutely true that using a threadpool lowers the runtime cost of using threads compared to creating and destroying threads all the time. Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: strange thing after call PyObject_CallMethod
Why this happenning and who makes Py_INCREF(self)? There are multiple possible explanations, but I think you have ruled out most of them: 1. on_recv might be returning self. So py_result would be the same as self, and hence be an additional reference. However, you said that on_recv raised an exception, so py_result should be NULL (can you confirm?) 2. there might be a reference leak in the implementation of on_recv. However, you say that it is all fine at the end, so this is unlikely 3. The implementation of on_recv stores the object inside another objects. There are too many possibilities for that to enumerate; here are some examples: def on_recv(self, buf): global foo, bar foo = self # creates global reference bar = self.on_send # creates bound method self.foo = self # creates cyclic reference foobar.append(self) # adds self into container If you are using gdb, I recommend to set a watchpoint on changes to ob_refcnt: (gdb) p ((PyObject*)self)-ob_refcnt $1 = (Py_ssize_t *) 0xa0cb5a0 (gdb) watch *(Py_ssize_t *) 0xa0cb5a0 Hardware watchpoint 2: *(ssize_t *) 168605088 (gdb) c Continuing. Hardware watchpoint 2: *(ssize_t *) 168605088 Old value = 2 New value = 1 0xb7d5f406 in list_clear (a=0xa041c74) at Objects/listobject.c:550 550 Py_XDECREF(item[i]); As you can see: this specific object was stored in a list, and the list is now being cleared. HTH, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: Noob question: Is all this typecasting normal?
On Jan 2, 10:50 pm, Ben Finney bignose+hates-s...@benfinney.id.au wrote: s0s...@gmail.com writes: On Jan 2, 7:20 pm, Ben Finney bignose+hates-s...@benfinney.id.au wrote: They don't need to be creative; they merely need to conform with the naming scheme as laid out in the PEP. If it's something to be included in the standard library, I agree (just for consistency, not because using_underscores is better). But for user code, I prefer mixedCase. That seems superficially like an easy distinction. Indeed, PEP 8 explicitly is meant to apply only to code intended for inclusion in the Python standard library. But consider: Python libraries generally don't get into the standard library until they've had a history of widespread public use as an external library. This helps ensure many of the harder-to-find wrinkles get discovered through wide exposure and ironed out before becoming standard. Code bases, especially library interfaces, that get a lot of use across wide communities are naturally going to have a whole lot of other people's code directly using those interfaces. Interfaces that are so widely used garner a high resistance to change, especially for something as non-functional as a naming convention. Choosing the naming convention for one's code is much easier to do when its usage base is smaller than when that base is larger. Therefore the easiest time to choose when to code in conformance to PEP 8 is right at the start. The best conclusion I can come to from this? Unless you explicitly *never* intend sharing your code with *anyone*, it's best to code all your Python code in accordance with PEP 8 anyway. You then don't have to make the decision about whether this is the time to follow PEP 8 or not; just do it by default, and you avoid the needless pain on those occasions, often unforeseeable at the start, where your code later ends up widely used. -- \ “One of the most important things you learn from the internet | `\ is that there is no ‘them’ out there. It's just an awful lot of | _o__) ‘us’.” —Douglas Adams | Ben Finney Fair enough, but for code that is not intended for general public usage (i.e., most code) so-called camelCase is every bit as good if not better than using underscores to divide variable names. It saves a few characters, and in my opinion it's significantly easier to read. Identifiers divided by underscores always appear to me at first glance to be multiple words, and I find that very annoying. So unless you think the standard library will someday include code for air traffic management, I'll stick with camelCase, and I'll thank you for not making an issue of it. As far as I am concerned, this is one of the most important bits of advice in PEP 8: A Foolish Consistency is the Hobgoblin of Little Minds -- http://mail.python.org/mailman/listinfo/python-list
Re: Doubt on creating threads
On Jan 3, 8:39 am, koranth...@gmail.com wrote: I was going through Python posts and this post caught my attentionhttp://groups.google.com/group/comp.lang.python/browse_thread/thread/... quote You have missed an important point. A well designed application does neither create so many threads nor processes. The creation of a thread or forking of a process is an expensive operation. You should use a pool of threads or processes. /unquote I am creating an application and it creates ~1-2 threads every second and kill it within 10 seconds. After reading this I am worried. Is creating a thread a very costly operation? I cannot use a pool of threads because I am using an external application (twisted) to create the threads (deferToThread). Generally you should only worry about this sort of thing if A) you actually notice a performance problem and B) testing indicates that it's thread creation which is causing it. Otherwise you could spend a lot of time working on something that doesn't actually affect your app's performance. ~S -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
Kless schrieb: How is possible that I can print a variable, but when I use *return var* it returns an empty string http://paste.pocoo.org/show/97588/ I don't see anything that indicates that the returned object is the empty string. Simply because there is no code testing for that. And of course you don't show any debugging output, which doesn't help either. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
On 3 ene, 19:12, Diez B. Roggisch de...@nospam.web.de wrote: Kless schrieb: How is possible that I can print a variable, but when I use *return var* it returns an empty string http://paste.pocoo.org/show/97588/ I don't see anything that indicates that the returned object is the empty string. Simply because there is no code testing for that. And of course you don't show any debugging output, which doesn't help either. Diez Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
On Jan 3, 11:20 am, Kless jonas@googlemail.com wrote: On 3 ene, 19:12, Diez B. Roggisch de...@nospam.web.de wrote: Kless schrieb: How is possible that I can print a variable, but when I use *return var* it returns an empty string http://paste.pocoo.org/show/97588/ I don't see anything that indicates that the returned object is the empty string. Simply because there is no code testing for that. And of course you don't show any debugging output, which doesn't help either. Diez Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' What? -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
On 3 ene, 19:40, Simon Forman sajmik...@gmail.com wrote: On Jan 3, 11:20 am, Kless jonas@googlemail.com wrote: Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' What? That's the output got from ipython. As you can see, it prints 'Afghanistan' but it can not returns it. In change, the another strings are returned. Could it be because it isn't returning the value from the recursivecall? -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
Kless schrieb: On 3 ene, 19:12, Diez B. Roggisch de...@nospam.web.de wrote: Kless schrieb: How is possible that I can print a variable, but when I use *return var* it returns an empty string http://paste.pocoo.org/show/97588/ I don't see anything that indicates that the returned object is the empty string. Simply because there is no code testing for that. And of course you don't show any debugging output, which doesn't help either. Diez Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' What is that? IPython? And I don't see no empty string here. *What* I see is the way python's interactive prompt puts out strings, like this: unicode(foo) u'foo' Do you mean by any chance that you don't understand why print prints foo, but the prompt shows ufoo? That is because the prompt invokes repr(o) to print out an object: print repr(unicode(foo)) u'foo' Which means that the output includes quotes and the u-prefix in case of an unicode object to help the user to see what the current object looks like. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
Kless schrieb: On 3 ene, 19:40, Simon Forman sajmik...@gmail.com wrote: On Jan 3, 11:20 am, Kless jonas@googlemail.com wrote: Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' What? That's the output got from ipython. As you can see, it prints 'Afghanistan' but it can not returns it. In change, the another strings are returned. Could it be because it isn't returning the value from the recursivecall? Yep, I guess that's the problem. You need to do if cell_tag: return clean_tags(cell_tag) Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
On Sat, 03 Jan 2009 11:46:10 -0800, Kless wrote: On 3 ene, 19:40, Simon Forman sajmik...@gmail.com wrote: On Jan 3, 11:20 am, Kless jonas@googlemail.com wrote: Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' What? That's the output got from ipython. As you can see, it prints 'Afghanistan' but it can not returns it. In change, the another strings are returned. Maybe you should show the *input* too… Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Returning a string
On 3 ene, 19:51, Diez B. Roggisch de...@nospam.web.de wrote: Kless schrieb: On 3 ene, 19:40, Simon Forman sajmik...@gmail.com wrote: On Jan 3, 11:20 am, Kless jonas@googlemail.com wrote: Afghanistan AF Out[19]: u'AF' AFG Out[19]: u'AFG' 004 Out[19]: u'004' What? That's the output got from ipython. As you can see, it prints 'Afghanistan' but it can not returns it. In change, the another strings are returned. Could it be because it isn't returning the value from the recursivecall? Yep, I guess that's the problem. You need to do if cell_tag: return clean_tags(cell_tag) Diez Thank you very much. It works now. -- http://mail.python.org/mailman/listinfo/python-list
Re: Reverse order of bit in repeating seqence of byte string
On Jan 2, 7:33 pm, John Machin sjmac...@lexicon.net wrote: For some very strange definition of works. You say you have 'bgr' and want to convert it to 'rbg'. The following code converts 'bgr' to 'rgb', which is somewhat more plausible, but not what you said you wanted. Well that's embarrassing ... you are correct. I need to convert from 'bgr' to 'rgb' Thanks to all others for suggestions FWIW, I realized the the C.types string buffer is/was mutable so settled on this; for start in xrange(0, ctypes.sizeof(buffer), 3): if buffer[start] != buffer[start+2]: #only need to swap the bits if they are different. ie if both are white or black, no change is required. blue, red = buffer[start], buffer[start+2] buffer[start], buffer[start+2] = red, blue This was about 30-40% faster that converting to list, processing and then converting back again. Will try the array module too ... but I think I need to find a new graphic package rather that makes working with the bits easier. g. -- http://mail.python.org/mailman/listinfo/python-list
Re: Noob question: Is all this typecasting normal?
for each his own. Any more word on userio? On Sat, Jan 3, 2009 at 6:14 PM, Russ P. russ.paie...@gmail.com wrote: On Jan 2, 10:50 pm, Ben Finney bignose+hates-s...@benfinney.id.aubignose%2bhates-s...@benfinney.id.au wrote: s0s...@gmail.com writes: On Jan 2, 7:20 pm, Ben Finney bignose+hates-s...@benfinney.id.aubignose%2bhates-s...@benfinney.id.au wrote: They don't need to be creative; they merely need to conform with the naming scheme as laid out in the PEP. If it's something to be included in the standard library, I agree (just for consistency, not because using_underscores is better). But for user code, I prefer mixedCase. That seems superficially like an easy distinction. Indeed, PEP 8 explicitly is meant to apply only to code intended for inclusion in the Python standard library. But consider: Python libraries generally don't get into the standard library until they've had a history of widespread public use as an external library. This helps ensure many of the harder-to-find wrinkles get discovered through wide exposure and ironed out before becoming standard. Code bases, especially library interfaces, that get a lot of use across wide communities are naturally going to have a whole lot of other people's code directly using those interfaces. Interfaces that are so widely used garner a high resistance to change, especially for something as non-functional as a naming convention. Choosing the naming convention for one's code is much easier to do when its usage base is smaller than when that base is larger. Therefore the easiest time to choose when to code in conformance to PEP 8 is right at the start. The best conclusion I can come to from this? Unless you explicitly *never* intend sharing your code with *anyone*, it's best to code all your Python code in accordance with PEP 8 anyway. You then don't have to make the decision about whether this is the time to follow PEP 8 or not; just do it by default, and you avoid the needless pain on those occasions, often unforeseeable at the start, where your code later ends up widely used. -- \ One of the most important things you learn from the internet | `\ is that there is no 'them' out there. It's just an awful lot of | _o__)'us'. —Douglas Adams | Ben Finney Fair enough, but for code that is not intended for general public usage (i.e., most code) so-called camelCase is every bit as good if not better than using underscores to divide variable names. It saves a few characters, and in my opinion it's significantly easier to read. Identifiers divided by underscores always appear to me at first glance to be multiple words, and I find that very annoying. So unless you think the standard library will someday include code for air traffic management, I'll stick with camelCase, and I'll thank you for not making an issue of it. As far as I am concerned, this is one of the most important bits of advice in PEP 8: A Foolish Consistency is the Hobgoblin of Little Minds -- http://mail.python.org/mailman/listinfo/python-list -- А-Б-В-Г-Д-Е-Ё-Ж-З-И-Й-К-Л-М-Н-О-П-Р-С-Т-У-Ф-Х-Ц-Ч-Ш-Щ-Ъ-Ы-Ь-Э-Ю-Я а-б-в-г-д-е-ё-ж-з-и-й-к-л-м-н-о-п-р-с-т-у-ф-х-ц-ч-ш-щ-ъ-ы-ь-э-ю-я -- http://mail.python.org/mailman/listinfo/python-list
ResponseNotReady exception
import httplib class Server: #server class def __init__(self, host): self.host = host def fetch(self, path): http = httplib.HTTPConnection(self.host) http.putrequest(GET, path) r = http.getresponse() print str(r.status) + : + r.reason server = Server(www.python.org) fp=open(phpvuln.txt) x=fp.readlines(); for y in x: server.fetch(/ + y); In the above code the phpvuln.txt file contains a list of directories. Why the above code throws ResponseNotReady exception ??? -- http://mail.python.org/mailman/listinfo/python-list
Re: select.select and socket.setblocking
Bryan Olson fakeaddr...@nowhere.org wrote: Where does this come up? Suppose that to take advantage of multi-core processors, our server runs as four processes, each with a single thread that responds to events via select(). Clients all connect to the same server port, so the socket listening on that port is shared by all four processes. A perfectly reasonable architecture (though with many more processes the simple implementation suffers the thundering herd problem). Which is why it is common for real world servers to serialize the select()/accept() code - usually via a file lock or a semaphore. -srp -- http://saju.net.in Two of our processors may be waiting on select() when a new connections comes in. The select() call returns in both processes, showing the socket ready for read, so both call accept() to complete the connection. The O.S. ensures that accept() [and recv()] are atomic, so one process gets the new connection; what happens in the other depends on whether we use a blocking or non-blocking socket, and clearly we want non-blocking. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: Noob question: Is all this typecasting normal?
Any more word on userio? None yet, I'm afraid. Should've started a different thread for it - but it's stuck here (in obscurity) forever xd. -- http://mail.python.org/mailman/listinfo/python-list
Re: strange thing after call PyObject_CallMethod
Thank you for so amazing debugging tutorial :). I owe you a beer. I found source of problem: then unhandled in python code exception occurs frame_dealloc() (Objects/frameobject.c:422) not called. Even if I call PyErr_Print(). But! If I call PyErr_Clear() then all okay! Docs says that both this functions clears error indicator... I hit a bug or my brains overheated? Some gdb output if you are intrested: Without exception: http://dpaste.com/104973/ With exception: http://dpaste.com/104975/ -- http://mail.python.org/mailman/listinfo/python-list
Re: ResponseNotReady exception
On Sat, Jan 3, 2009 at 12:38 PM, asit lipu...@gmail.com wrote: import httplib class Server: #server class def __init__(self, host): self.host = host def fetch(self, path): http = httplib.HTTPConnection(self.host) http.putrequest(GET, path) According to the docs, if you use .putrequest(), you have to also then call .putheader() [as many times as necessary], .endheaders(), and .send(), in that order. I'd advise just changing .putrequest() to .request() instead. And you should also read the fine docs yourself: http://docs.python.org/library/httplib.html Cheers, Chris -- Follow the path of the Iguana... http://rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Port of python stdlib to other languages.
Have there been ports of the Python standard library to other languages? I would imagine using pickle, urllib, and sys in C (with pythonic naming conventions) would be easier than using other libraries to do the same thing. -- http://mail.python.org/mailman/listinfo/python-list
Re: Port of python stdlib to other languages.
vk schrieb: Have there been ports of the Python standard library to other languages? I would imagine using pickle, urllib, and sys in C (with pythonic naming conventions) would be easier than using other libraries to do the same thing. AFAIK not. You could try elmer (found on SF) to expose these as C-DLL. However, I doubt this will be widely adopted - to much hassle, especially for OO-style interfaces. Those aren't properly exposable. What do you need C for anyway? Or, to put it the other way round - why not expose whatever you need in C as python extension, and write your app in Python? Diez -- http://mail.python.org/mailman/listinfo/python-list
win32gui
Hi, I'm trying to capture the text word under the user cursor, so I was searching the win32 lib for functions I can use. i used this to fined the controller under the cursor win32gui.WindowFromPoint(win32gui.GetCursorPos()) to get the controller, but then when I try to read the text with this GetWindowText function it most of the time doesn't work, all the getline methon like the following didn't worked in most of the time too win32gui.SendMessage(hwnd, win32con.EM_GETLINE, line, linetext) I found this GetCharFromPosition in a VB forum which sound promising but unfortunately it's not part of the win32gui for python so now i'm looking for a reliable way to rich text from a controller or position if you know a function who may do it or a better way please tell me/ thank you and have a nice day -- http://mail.python.org/mailman/listinfo/python-list
Re: ResponseNotReady exception
On Jan 4, 1:59 am, Chris Rebert c...@rebertia.com wrote: On Sat, Jan 3, 2009 at 12:38 PM, asit lipu...@gmail.com wrote: import httplib class Server: #server class def __init__(self, host): self.host = host def fetch(self, path): http = httplib.HTTPConnection(self.host) http.putrequest(GET, path) According to the docs, if you use .putrequest(), you have to also then call .putheader() [as many times as necessary], .endheaders(), and .send(), in that order. I'd advise just changing .putrequest() to .request() instead. And you should also read the fine docs yourself:http://docs.python.org/library/httplib.html Cheers, Chris -- Follow the path of the Iguana...http://rebertia.com Thanx -- http://mail.python.org/mailman/listinfo/python-list
compiling python2.5 on linux under wine
hey, has anyone investigated compiling python2.5 using winegcc, under wine? i'm presently working my way through it, just for kicks, and was wondering if anyone would like to pitch in or stare at the mess under a microscope. it's not as crazed as it sounds. cross-compiling python2.5 for win32 with mingw32 is an absolute miserable bitch of a job that goes horribly wrong when you actually try to use the minimalist compiler to do any real work. so i figured that it would be easier to get python compiled using wine. i _have_ got some success - a python script and a python.exe.so (which is winegcc's friendly way of telling you you have something that stands a chance of working) as well as a libpython25.dll.so. what i _don't_ yet have is an _md5.dll (or should it be _md5.lib?) i.e. the standard modules are a bit... iffy. the _winreg.o is compiled; the _md5.o is compiled; the winreg.lib is not. whoops. plus, it's necessary to enable nt_dl.c which is in PC/ _not_ in Modules/. one of the key issues that's a bit of a bitch is that python is compiled up for win32 with a hard-coded pyconfig.h which someone went to a _lot_ of trouble to create by hand instead of using autoconf. oh - and it uses visualstudio so there's not even a Makefile. ignoring that for the time-being was what allowed me to get as far as actually having a python interpreter (with no c-based modules). so there's a whole _stack_ of stuff that needs dragging kicking and screaming into the 21st century. there _is_ a reason why i want to do this. actually, there's two. firstly, i sure as shit do _not_ want to buy, download, install _or_ run visual studio. i flat-out refuse to run an MS os and visual studio runs like a dog under wine. secondly, i want a python25.lib which i can use to cross-compile modules for poor windows users _despite_ sticking to my principles and keeping my integrity as a free software developer. thirdly i'd like to cross-compile pywebkitgtk for win32 fourthly i'd like to compile and link applications to the extremely successful and well wicked MSHTML.DLL... in the _wine_ project :) not the one in windows (!) i want to experiment with DOM model manipulation - from python - similar to the OLPC HulaHop project - _but_ i want to compile or cross-compile everything from linux, not windows (see 1 above) fifthly i'd like to see COM (DCOM) working and pywin32 compiled and useable under wine, even if it means having to get a license to use dcom98 and oleauth.lib and oleauth.h etc. and all the developer files needed to link DCOM applications under windows. actually what i'd _really_ like to see is FreeDCE's DCOM work actually damn well finished, it's only been eight years since wez committed the first versions of the IDL and header files, and it's only been over fifteen years since microsoft began its world domination using COM and DCOM. ... but that's another story :) so that's ... five reasons not two. if anyone would like to collaborate on a crazed project with someone who can't count, i'm happy to make available what i've got up to so far, on github.org. l. -- http://mail.python.org/mailman/listinfo/python-list
Re: select.select and socket.setblocking
Bryan Olson fakeaddr...@nowhere.org wrote: There are cases where a socket can select() as readable, but not be readable by the time of a following recv() or accept() call. All such cases with which I'm familiar call for a non-blocking socket. I used to believe that if select() said data was ready for reading, a subsequent read/recv/recvfrom() call could not block. It could return an error, but it could not block. I was confident of this until just a few months ago when reality blew up in my face. The specific incident involved a bug in the linux kernel. If you received an UDP packet with a checksum error, the select() would return when the packet arrived, *before* the checksum was checked. By the time you did the recv(), the packet had been discarded and the recv() would block. This led me on a big research quest (including some close readings of Stevens, which appeared to say that this couldn't happen). The more I read, the more I (re) discovered just how vague and poorly written the Berkeley Socket API docs are :-) The bottom line is that Bryan is correct -- regardless of what the various man pages and textbooks say, in the real world, it is possible for a read() to block after select() says the descriptor is ready. The right way to think about select() is to treat it as a heuristic which can make a polling loop more efficient, but should never be relied upon to predict the future. Neither the negative nor positive behavior is guaranteed. There's no guaranteed response time; just because select() hasn't returned yet doesn't mean a descriptor couldn't be read without blocking in another thread right now. And, just because it has returned, that doesn't mean by the time you get around to reading, there will still be anything there. -- http://mail.python.org/mailman/listinfo/python-list
Re: math module for Decimals
On Dec 31 2008, 11:02 pm, Steven D'Aprano st...@remove-this- cybersource.com.au wrote: On Sun, 28 Dec 2008 06:38:32 -0800, Mark Dickinson wrote: On Dec 28, 7:28 am, Steven D'Aprano st...@remove-this- cybersource.com.au wrote: Ah crap, I forgot that from_float() has been left out of the decimal API. That's very annoying. Agreed. It's maybe even annoying enough that a feature request at bugs.python.org might be honoured. (Hint, hint!) I can take a hint :) http://bugs.python.org/issue4796# Decimal.from_float() implemented by Raymond Hettinger for Python 2.7 and Python 3.1, within 72 hours of Steven submitting the feature request. If only all issues could be resolved this quickly. :-) Mark -- http://mail.python.org/mailman/listinfo/python-list
Re: math module for Decimals
On Jan 3, 9:27 pm, Mark Dickinson dicki...@gmail.com wrote: Decimal.from_float() implemented by Raymond Hettinger for Python 2.7 and Python 3.1, within 72 hours of Steven submitting the feature request. If only all issues could be resolved this quickly. :-) Rats. I left out the crucial line of that post, namely: Thank you, Steven! -- http://mail.python.org/mailman/listinfo/python-list
Re: Reverse order of bit in repeating seqence of byte string
On Jan 4, 7:10 am, imageguy imageguy1...@gmail.com wrote: On Jan 2, 7:33 pm, John Machin sjmac...@lexicon.net wrote: For some very strange definition of works. You say you have 'bgr' and want to convert it to 'rbg'. The following code converts 'bgr' to 'rgb', which is somewhat more plausible, but not what you said you wanted. Well that's embarrassing ... you are correct. I need to convert from 'bgr' to 'rgb' Thanks to all others for suggestions FWIW, I realized the the C.types string buffer is/was mutable so settled on this; for start in xrange(0, ctypes.sizeof(buffer), 3): if buffer[start] != buffer[start+2]: #only need to swap the bits if they are different. ie if both are white or black, no change is required. blue, red = buffer[start], buffer[start+2] buffer[start], buffer[start+2] = red, blue You are likely find that using buffer[start], buffer[start+2] = buffer[start+2], buffer[start] is faster. Cheers, John -- http://mail.python.org/mailman/listinfo/python-list
deleting a method
I am trying to delete a method from a class. It's easy to delete other attributes, but when I try: class A: ... def foo(): ... pass ... a = A() del a.foo I get Traceback (most recent call last): File stdin, line 1, in module AttributeError: A instance has no attribute 'foo' Why is it so and how may still delete it? -- Filip Gruszczyński -- http://mail.python.org/mailman/listinfo/python-list
Re: deleting a method
Filip Gruszczyński wrote: I am trying to delete a method from a class. It's easy to delete other attributes, but when I try: class A: ... def foo(): ... pass ... a = A() del a.foo I get Traceback (most recent call last): File stdin, line 1, in module AttributeError: A instance has no attribute 'foo' Why is it so and how may still delete it? 'a' is an instance of class A. You're trying to delete 'foo' from the instance. -- http://mail.python.org/mailman/listinfo/python-list
Re: deleting a method
MRAB goo...@mrabarnett.plus.com writes: Filip Gruszczyński wrote: Traceback (most recent call last): File stdin, line 1, in module AttributeError: A instance has no attribute 'foo' Why is it so and how may still delete it? 'a' is an instance of class A. You're trying to delete 'foo' from the instance. To answer the second question: since ‘foo’ is an attribute of the class ‘A’, you can delete the attribute from the class. class A(object): ... def foo(self): ... pass ... a = A() 'foo' in dir(a) True del A.foo 'foo' in dir(a) False -- \ “If you don't know what your program is supposed to do, you'd | `\ better not start writing it.” —Edsger W. Dijkstra | _o__) | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Testing if an index is in a slice
ajaksu wrote: On Jan 1, 4:12 pm, mma...@gmx.net wrote: I would like to check if an index is in a slice or not without iterating over the slice. Something like: isinslice(36, slice(None, 34, -1)) True I think it'd be feasible for slices that can be mapped to ranges[1], but slices are more flexible than that. If we add a parameter for the length of the list to which the slice is applied, then inslice() is well-defined. I thought it would easy to write, but that was hours ago when I knew less about Python slice indexing than I do now. And I thought I new a bunch from writing a virtual slice class. I'm leaning towards mmanns' idea that this should be built in. Handling all the cases is remarkably tricky. Here's a verbose version, with a little test: def inslice(i, slc, length): Would index i be part of slice slc of a list of len length? step = slc.step or 1 if step 0: if slc.start is None: start = 0 elif slc.start = 0: start = slc.start else: start = max(0, length + slc.start) if slc.stop is None: stop = length elif slc.stop = 0: stop = min(length, slc.stop) else: stop = length + slc.stop return start = i stop and (i - start) % step == 0 else: if slc.start is None: start = length - 1 elif slc.start = 0: start = min(length - 1, slc.start) else: start = length + slc.start if slc.stop is None: stop = -1 elif slc.stop = 0: stop = slc.stop else: stop = max(-1, length + slc.stop) return start = i stop and (start - i) % (-step) == 0 # test for start in [None, 0, 1, -1, -3, 4]: for stop in [None, 0, 1, -1, 3, -5]: for step in [None, 1, -1, 2, -3]: for n in [0, 1, 2, 3, 5, 11, 16]: slc = slice(start, stop, step) s1 = [i for i in range(-3, n + 5) if inslice(i, slc, n)] s2 = sorted(range(n)[slc]) assert s1 == s2 -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: why cannot assign to function call
On Jan 3, 11:25 am, John O'Hagan resea...@johnohagan.com wrote:
On Tue, 30th Dec 2008, Aaron Brady wrote:
Accepting that, I'll adopt the terms John proposed, 'change' vs.
'exchange', the former when the material configuration changes, the
latter when the communication axioms change.
b= [2, 3]
b= [3, 4]
'b' has exchanged. (Somewhat ungrammatical.)
b= [2, 3]
b.append( 4 )
'b' has changed.
According to this, when you replace every floorboard on a porch, one
at a time, it's still the same porch-- it's changed, it's different,
and it's the same. However, if you haul off the porch and put a new
one in its place, it's not. ('porch[:]=' vs. 'porch='.) You can't
just look at the initial and final configurations of matter to
determine so. Therefore, 'id' is an informal function.
This analogy describes the ontological minefield I was referring to in a
previous post in this thread (which has expired in my mail reader, so my
apologies if the threading goes awry): In what sense is a porch (or list, or
string) the same if all (or even some of) its parts have been exchanged?
I think the answer is something to do with the abstraction, the container,
the instance of the class. Would it be fair to say that perhaps there are no
truly mutable objects, only immutable containers whose contents (also
immutable objects themselves) may be exchanged? Or to pose the question
another way, are objects only mutable insofar as they are composite?
As you argue above, the planks are not the porch; I would add that it's your
_decision_ to build (or tear down) a porch which makes it _that_ particular
porch (or not).
As you imply above (I think), you have to keep looking (or someone does,
presumably the interpreter) to know whether an object is the same as or just
equal to another (which starts to sound spookily like the role of the
observer in phenomenology or quantum physics). Whether this means that id()
is informal or not, I'll leave to others better informed than I.
Regards,
John
I think the key ingredient is that there's no such thing as side
effect in math.
In example,
a= [0, 1, 2]
a[:]= [3, 4, 5]
There aren't many natural language senses in which 'a' is the same
object as before. If I have a leg transplant, I'm the same person,
but if you replace the entire contents of me, I'm not. But 'a' is.
The porch is defined by its location, but not exclusively. Natural
language identity is a cluster concept, without strict necessary and
sufficient conditions. Nothing really presses our boundaries of it
that much; there aren't many practical questions that lay out the
facts, then ask, 'But is it the same?' You can replace the porch
board-at-a-time, and it is; and you can haul it somewhere and it is.
But rearrange the same boards, and it's not. Continuity of form is
probably the prevalent feature, which as you state, does break down in
the case of composite (piece-wise) transformations.
You might get farther comparing container objects to spots on a
bulletin board. The only thing that goes 'in' a container is a
denoting phrase to another object (and by the way, not a description);
the other also has its own spot independently on the board.
It's not clear IMO that the question is so much a minefield-- a
question that it's really easy to get throw (fall) off course
pursuing, as it is that there's no such course. In short, there is no
such thing as composite identity, only matter; or in Python, only
spots on the bulletin board.
Or to pose the question
another way, are objects only mutable insofar as they are composite?
No; tuples are composite. If I flip one bit in a byte somewhere, is
it the same byte?
--
http://mail.python.org/mailman/listinfo/python-list
Re: socket send help
Gabriel Genellina wrote: greyw...@gmail.com escribió: [...] A simple server: from socket import * myHost = '' Try with myHost = '127.0.0.1' instead - a firewall might be blocking your server. Just a nit: I'd say the reason to use '127.0.0.1' instead of the empty string is that a firewall might *not* be blocking your server. The Python sockets module interprets the empty string as INADDR_ANY, which means to bind to all available adapters including the loopback, A.K.A localhost, A.K.A '127.0.0.1'. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: Doubt on creating threads
koranth...@gmail.com wrote: I am creating an application and it creates ~1-2 threads every second and kill it within 10 seconds. After reading this I am worried. Is creating a thread a very costly operation? Compared to a procedure call it's expensive, but a couple threads per second is insignificant. My out-dated Pentium 4 desktop can create and destroy a few thousand threads per second under WinXP; more under recent Linux. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
Re: Noob question: Is all this typecasting normal?
On Sat, 03 Jan 2009 20:35:25 +, alex goretoy wrote: for each his own. Please don't top-post. Please don't quote the ENTIRE body of text (PLUS doubling it by including a completely useless HTML version) just to add a trivial comment. Trim the text you are replying to. Any more word on userio? I doubt many people care about it. Why don't you write it, put it up on the Cheeseshop, and see if anyone uses it? Just because you think it is useful doesn't mean others do, but if they do, then great. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: math module for Decimals
On Sat, 03 Jan 2009 13:34:11 -0800, Mark Dickinson wrote: On Jan 3, 9:27 pm, Mark Dickinson dicki...@gmail.com wrote: Decimal.from_float() implemented by Raymond Hettinger for Python 2.7 and Python 3.1, within 72 hours of Steven submitting the feature request. If only all issues could be resolved this quickly. :-) Rats. I left out the crucial line of that post, namely: Thank you, Steven! And many thanks to both you and Raymond, firstly for doing the actual work, and secondly for your patience with my questions on the bug tracker. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Noob question: Is all this typecasting normal?
On Sat, 03 Jan 2009 16:19:58 +0100, Bruno Desthuilliers wrote: But indeed, you obviously cannot add strings with numerics nor concatenate numerics with strings. This would make no sense. The OP comes from a Perl background, which AFAIK allows you to concat numbers to strings and add strings to numbers. That's probably the (mis) feature he was hoping Python had. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Why not Ruby?
On Jan 1, 3:55 am, Roger rdcol...@gmail.com wrote: On Dec 31, 12:55 pm, Xah Lee xah...@gmail.com wrote: Just spent 3 hours looking into Ruby today. Here's my short impression for those interested. Who are you? In case no one tells you, you are a cocky, egotistical windbag with opinions that border constructive but never gets there. Why would anyone care what you think? Again, who are you? Xah Lee? And? I didn't subscribe to read reviews on Ruby. And I'm pretty sure anyone that bothers to subscribe to a group about programming has the wherewithal to research a language themselves and come to their own determiniation. Also, this is a Python group and not Ruby. I knew I should have avoided this post and read the one about Nike Shoes from China. At least those bits of trolling spam don't try to mask themselves as something worthwhile. agree with you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Ideas to optimize this getitem/eval call?
On Sat, 03 Jan 2009 04:14:14 -0800, mario wrote: On Jan 3, 7:16 am, Steven D'Aprano st...@remove-this- cybersource.com.au wrote: [...] I must say though, your choice of builtins to prohibit seems rather arbitrary. What is dangerous about (e.g.) id() and isinstance()? Preventive, probably. I also feel that temlates should have any business with info such as the memory addressed returnred by id(). For isinstance, becuase it is somewhat related to __subclasses__ that is known to be insecure. It's that probably that worries me. In my earlier post, I was going to say your choice of builtins to prohibit seems rather Cargo Cult-ish, but I decided that might be a bit rude, and I decided to give you the benefit of the doubt. But your answer here doesn't really give me any more confidence. What security issues do you think you are preventing by prohibiting id()? It is true that the id returned is a memory address in CPython, but that's a mere implementation detail, and may not be true in other implementations. Even if it is a memory address, so what? You can't do anything with it except treat it as an integer. I don't see how id() decreases security one iota. In the absence of even a theoretical threat, banning a function that returns an int because the int is derived from a memory address (but can't be used as one!) makes you appear to be engaging in Cargo Cult programming: following the ritual, without any understanding of what you are doing. http://catb.org/~esr/jargon/html/C/cargo-cult-programming.html Sorry to be so harsh, especially over such a tiny little thing as the id() function, but that's the impression it gives me, and I'm probably not the only one. It is true that a false positive (needlessly banning a harmless function) has less serious consequences than a false negative (failing to ban a harmful function), but it does reduce confidence that you know what you're doing. Likewise for isinstance() and issubclass(). They may be related to __subclasses__, but they don't give the caller access to __subclassess__. So what is the actual threat you are defending against? I'm not saying that there must be an actual in-the-wild demonstrated vulnerability before you prohibit a built-in, but there should be at least a plausible attack vector. Incidentally, I updated the page you point to clarify what is going on. Speaking of that page, you have an obvious typo (teh instead of the) that should be fixed: In addition to teh above, all subclasses of BaseException... http://evoque.gizmojo.org/usage/restricted/ I also added a link to Brett Cannon's inspiration paper on the topic of securing the python interpreter... except: # KeyError, NameError, AttributeError, SyntaxError, # ValueError, TypeError, IOError If you want to capture seven exceptions, then capture seven exceptions, not any exception. Absolutely not. I want to catch ALL evaluation exceptions... I see. It wasn't clear that this was deliberate, I read it as if there was a fixed, finite list you wanted to catch, and nothing else. You should make sure this is clearly documented in your code. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: strange behavior of math.sqrt() in new 3.0 version
Tim Roberts wrote: Scott David Daniels scott.dani...@acm.org wrote: I avoid using single-letter variables except where I know the types from the name (so I use i, j, k, l, m, n as integers, s as string, and w, x, y, and z I am a little looser with (but usually float or complex). It's amazing to me that Fortran continues to live on in the hearts and minds of today's programmers. Fortran is alive and well. If you can find a Fortran 2003 compiler, you can even use classes. -- http://mail.python.org/mailman/listinfo/python-list
Re: When does python 3.1， 3.2 version out？
On Jan 3, 8:47 pm, 叮叮当当 guoti...@gmail.com wrote: Now， the 3.0 version is out for a time. I wonder when the python 3.1 is out, and what change is in python 3.1. There's no schedule yet. Hopefully, one will come into being around PyCon. -- http://mail.python.org/mailman/listinfo/python-list
simple turn-based multiplayer game via TCP server/client
Hi everyone,
I'm learning python to get a multiplayer roleplaying game up and
running.
I didn't see any simple examples of multiplayer games on the web so I
thought I'd post mine here. I choose Rock, Paper, Scissors as a first
game to experiment with as the game logic/options are easy to
implement and understand.
Initially, I tried to get the socketserver.TCPServer example in the
Python Docs to work, but couldn't get my game variables into the
handle method of the class MyTCPHandler. And I didn't know how else
to do it. I ended up creating my own server client out of simple
sockets based on the simple echo server client examples in the
Python Docs.
I also wanted to send chat messages OR game variables back forth,
but I couldn't figure out how to do the OR, so the basic idea in this
implementation is to send the dictionary 'game' back and forth. game
dict contains all the gaming variables as well as any chat messages.
The program processes results depending on whether the game is
starting, there's a chat message, or there's a game move.
Finally, in testing, I ran the server in IDLE, but I had to load a
command prompt and switch to c:\python30; then type 'python
rpsmulti.py' for the client every time. Anyone know how to test
server/client code strictly in IDLE?
Anyway, try it out and let me know how you would improve it.
John R.
# NAME: rpsmulti.py
# DESCRIPTION: rock, paper, scissors game multiplayer game
# AUTHOR: John Robinson
# DATE: 1/3/09
# VERSION: Python 3.0
# TO DO:
# .server_address instead of HOST, PORT?
import socket
from random import choice
from pickle import dumps, loads
from pprint import pprint
HOST, PORT = localhost, # defined for now
BUFFSIZE = 1024 # for socket.send recv commands
BACKLOG = 2 # number of clients supported by
server
SECONDS = 3 # seconds until socket.timeout (not
implemented)
# moves dict to translate 'rps' choice
MOVES = {'r':'Rock',
'p':'Paper',
's':'Scissors'}
# outcome dict stores result for all possible scenarios
OUTCOME = {('p','r'): 'win',
('r','s'): 'win',
('s','p'): 'win',
('p','p'): 'draw',
('r','r'): 'draw',
('s','s'): 'draw',
('r','p'): 'lose',
('s','r'): 'lose',
('p','s'): 'lose'}
def main_menu(game):
initialize game dict variables opening screen of the game
game['total'] = 0 # total number of games played
game['won'] = 0 # total games won by player
game['lost'] = 0# total games lost by player
game['drew'] = 0# total games drew by player
game['move'] = '' # player's move (rps)
game['message'] = ''# player's chat message
game['sentmessage'] = ''# player's previous message
game['start'] = True# setting up the game boolean
print(\tROCK PAPER SCISSORS\n)
if game['name']=='':# if returning to menu don't display
the following
game['name'] = get_name()
print(Welcome +game['name']+. Remember...)
print(Rock smashes scissors! Paper covers Rock! Scissors cuts
paper!\n)
print(1. Play single player game)
print(2. Start two player game)
print(3. Join two player game)
print(4. Quit)
print()
c = safe_input(Your choice? , 1234)
c = int(c)
if c==1:
one_player(game)
elif c==2:
start_two_player(game)
elif c==3:
two_player_join(game)
else:
print('Play again soon.')
def safe_input(prompt, values='abcdefghijklmnopqrstuvwxyz'):
gives prompt, checks first char of input, assures it meets
given values
default is anything goes
while True:
i = input(prompt)
try:
c = i[0].lower()
except IndexError: # the only possible error?!
if c=='':
print(Try again.)
else:
if c not in values: # some other character
print(Try again.)
else: # looks good. continue.
break
return i
def get_name():
returns input as name
while True:
name = input(What is your name? )
check = input(name + . Correct (y/n)? )
if check[0] in 'yY':
break
return name
def get_result(player, opponent):
reports opponent's choice;
checks player and opponent dicts ['move'] against OUTCOME
dict;
reports result
returns player dict with updated values
print(opponent['name'], 'chose %s.' % (MOVES[opponent['move']]))
# check lookout dict (OUTCOME dictionary)
result = OUTCOME[(player['move'], opponent['move'])]
# update game variables
player['total'] += 1
if result=='win':
print('%s beats %s. You win.' % (MOVES[player['move']], MOVES
[opponent['move']]))
player['won'] += 1
elif result=='draw':
print('%s - %s: no one wins. You draw.' % (MOVES[player
Re: win32gui
Gandalf goldn...@gmail.com wrote: I'm trying to capture the text word under the user cursor, so I was searching the win32 lib for functions I can use. You should know that, in the general case, this is impossible. Remember that the screen image you are looking at is just a big array of dots. If the window underneath happens to be an image, there won't be any text to fetch. Now, in many cases it IS possible, but it's not easy. i used this to fined the controller under the cursor win32gui.WindowFromPoint(win32gui.GetCursorPos()) to get the controller, That's the first step. Then, you need to figure out what kind of window it is. If it is a standard edit box, you can use the EM_GETLINE functions. If it's a rich text edit box, you can use the rich text messages. -- Tim Roberts, t...@probo.com Providenza Boekelheide, Inc. -- http://mail.python.org/mailman/listinfo/python-list
Re: Port of python stdlib to other languages.
AFAIK not. You could try elmer Elmer looks very interesting, but not really what I was getting at. What do you need C for anyway? Or, to put it the other way round - why not expose whatever you need in C as python extension, and write your app in Python? I'm not looking to write a Python app atm. Just curious if someone had started a project like this, to, say, make Python users more comfortable using other languages (for whatever reason), or allow other people to try python-like code in their language to see if it suits them. -- http://mail.python.org/mailman/listinfo/python-list
Re: Doubt on creating threads
On Jan 4, 4:59 am, Bryan Olson fakeaddr...@nowhere.org wrote: koranth...@gmail.com wrote: I am creating an application and it creates ~1-2 threads every second and kill it within 10 seconds. After reading this I am worried. Is creating a thread a very costly operation? Compared to a procedure call it's expensive, but a couple threads per second is insignificant. My out-dated Pentium 4 desktop can create and destroy a few thousand threads per second under WinXP; more under recent Linux. -- --Bryan Thank you very much. I was worried about this a lot. -- http://mail.python.org/mailman/listinfo/python-list
Re: Port of python stdlib to other languages.
On Jan 3, 10:15�pm, vk vmi...@gmail.com wrote: AFAIK not. You could try elmer Elmer looks very interesting, but not really what I was getting at. What do you need C for anyway? Or, to put it the other way round - why not expose whatever you need in C as python extension, and write your app in Python? I'm not looking to write a Python app atm. Just curious if someone had started a project like this, to, say, make Python users more comfortable using other languages (for whatever reason), or allow other people to try python-like code in their language to see if it suits them. But wouldn't your language of choice first have to support things like lists, generators, etc.? I can use GMP library in C instead of gmpy in Python, but not if I need to use Python things that I don't know how to implement in C. -- http://mail.python.org/mailman/listinfo/python-list
Memoizing and WeakValueDictionary
Just wanted to share some experience I had in doing some memory and performance tuning of a graphics script. I've been running some long- running scripts on high-resolution images, and added memoizing to optimize/minimize object creation (my objects are immutable, so better to reuse objects from a cache than constantly create and discard instances). This helped my script early on, but as the data files got larger and larger, and runs got longer and longer, the object memoize cache started to suck up some serious memory, and performance started to degrade for a different reason - low memory - page thrashing - program crawling. It occurred to me that in my program, a given object may get used for a while, but once its use declines, it doesn't come back for a while. At first blush, I thought about using some sort of LRU cache, but first I tried the WeakValueDictionary from the wkref module. This worked great! Now I get fairly optimal reuse of my immutable instances, but my object cache doesn't grow without bounds. Does this sound like a correct interpretation of this behavior? If so, it would seem that WeakValueDictionary would be a good recommendation to go along with any memoizing implementations. -- http://mail.python.org/mailman/listinfo/python-list
Re: simple turn-based multiplayer game via TCP server/client
Since we are on the subject of Rock, Paper, Scissors. I've recntly watched
this one video on how to make a .deb out of .py files and the tutor was
using a rock, paper scissors game.
Not sure how this may come of use to you but, I'll post it anyway for you to
look at. May help somehow.
http://www.google.com/search?hl=enq=filetype%3Apy+%22rock+paper+scissors%22btnG=Search
http://www.showmedo.com/videos/video?name=linuxJensMakingDebfromSeriesID=37
Hope this help you in your journey for multiplayer game somehow
On Sun, Jan 4, 2009 at 3:58 AM, greyw...@gmail.com greyw...@gmail.comwrote:
Hi everyone,
I'm learning python to get a multiplayer roleplaying game up and
running.
I didn't see any simple examples of multiplayer games on the web so I
thought I'd post mine here. I choose Rock, Paper, Scissors as a first
game to experiment with as the game logic/options are easy to
implement and understand.
Initially, I tried to get the socketserver.TCPServer example in the
Python Docs to work, but couldn't get my game variables into the
handle method of the class MyTCPHandler. And I didn't know how else
to do it. I ended up creating my own server client out of simple
sockets based on the simple echo server client examples in the
Python Docs.
I also wanted to send chat messages OR game variables back forth,
but I couldn't figure out how to do the OR, so the basic idea in this
implementation is to send the dictionary 'game' back and forth. game
dict contains all the gaming variables as well as any chat messages.
The program processes results depending on whether the game is
starting, there's a chat message, or there's a game move.
Finally, in testing, I ran the server in IDLE, but I had to load a
command prompt and switch to c:\python30; then type 'python
rpsmulti.py' for the client every time. Anyone know how to test
server/client code strictly in IDLE?
Anyway, try it out and let me know how you would improve it.
John R.
# NAME: rpsmulti.py
# DESCRIPTION: rock, paper, scissors game multiplayer game
# AUTHOR: John Robinson
# DATE: 1/3/09
# VERSION: Python 3.0
# TO DO:
# .server_address instead of HOST, PORT?
import socket
from random import choice
from pickle import dumps, loads
from pprint import pprint
HOST, PORT = localhost, # defined for now
BUFFSIZE = 1024 # for socket.send recv commands
BACKLOG = 2 # number of clients supported by
server
SECONDS = 3 # seconds until socket.timeout (not
implemented)
# moves dict to translate 'rps' choice
MOVES = {'r':'Rock',
'p':'Paper',
's':'Scissors'}
# outcome dict stores result for all possible scenarios
OUTCOME = {('p','r'): 'win',
('r','s'): 'win',
('s','p'): 'win',
('p','p'): 'draw',
('r','r'): 'draw',
('s','s'): 'draw',
('r','p'): 'lose',
('s','r'): 'lose',
('p','s'): 'lose'}
def main_menu(game):
initialize game dict variables opening screen of the game
game['total'] = 0 # total number of games played
game['won'] = 0 # total games won by player
game['lost'] = 0# total games lost by player
game['drew'] = 0# total games drew by player
game['move'] = '' # player's move (rps)
game['message'] = ''# player's chat message
game['sentmessage'] = ''# player's previous message
game['start'] = True# setting up the game boolean
print(\tROCK PAPER SCISSORS\n)
if game['name']=='':# if returning to menu don't display
the following
game['name'] = get_name()
print(Welcome +game['name']+. Remember...)
print(Rock smashes scissors! Paper covers Rock! Scissors cuts
paper!\n)
print(1. Play single player game)
print(2. Start two player game)
print(3. Join two player game)
print(4. Quit)
print()
c = safe_input(Your choice? , 1234)
c = int(c)
if c==1:
one_player(game)
elif c==2:
start_two_player(game)
elif c==3:
two_player_join(game)
else:
print('Play again soon.')
def safe_input(prompt, values='abcdefghijklmnopqrstuvwxyz'):
gives prompt, checks first char of input, assures it meets
given values
default is anything goes
while True:
i = input(prompt)
try:
c = i[0].lower()
except IndexError: # the only possible error?!
if c=='':
print(Try again.)
else:
if c not in values: # some other character
print(Try again.)
else: # looks good. continue.
break
return i
def get_name():
returns input as name
while True:
name = input(What is your name? )
check = input(name + . Correct (y/n)? )
if check[0] in 'yY':
break
return name
def
Re: why cannot assign to function call
I'm answering both John and Aaron's comments in the following. Mostly
John at the start, Aaron toward the end.
On Sat, 03 Jan 2009 15:42:47 -0800, Aaron Brady wrote:
On Jan 3, 11:25 am, John O'Hagan resea...@johnohagan.com wrote:
[...]
According to this, when you replace every floorboard on a porch, one
at a time, it's still the same porch-- it's changed, it's different,
and it's the same. However, if you haul off the porch and put a new
one in its place, it's not. ('porch[:]=' vs. 'porch='.) You can't
just look at the initial and final configurations of matter to
determine so. Therefore, 'id' is an informal function.
This analogy describes the ontological minefield I was referring to
in a previous post in this thread (which has expired in my mail
reader, so my apologies if the threading goes awry): In what sense is
a porch (or list, or string) the same if all (or even some of) its
parts have been exchanged?
I think the answer is something to do with the abstraction, the
container, the instance of the class.
That seems reasonable. When you say alist[:] = [1, 2, 3] the container
remains the same, while the contents change.
Would it be fair to say that perhaps there are no
truly mutable objects, only immutable containers whose contents (also
immutable objects themselves) may be exchanged? Or to pose the
question another way, are objects only mutable insofar as they are
composite?
That depends on what you mean by composite. Everything is composite in
some sense, even a single bit in memory has a physical reality made of
atoms with magnetic fields. But taken as an abstract entity, it is
reasonable to treat a single bit as an atomic non-composite thing, and a
single bit is mutable.
In practice, actual Python objects tend to be mutable only if they are
composite (although being composite doesn't make them mutable -- consider
frozen sets and tuples). In principle, this is not necessary. There's no
reason why Python couldn't expose a single bit as a data type, so you
could write this:
n = bit(1)
bool(n)
True
n.flip()
bool(n)
False
As you argue above, the planks are not the porch; I would add that
it's your _decision_ to build (or tear down) a porch which makes it
_that_ particular porch (or not).
No, there's no such decision needed. Perhaps a hurricane comes through
and rips the porch up. Maybe a rogue television crew comes by while
you're at work and renovates your house without your knowledge.
The lack of decision-making needed is more obvious when you consider
something like a fast-flowing river. The specific water molecules making
up the river at any particular instant in time flow away in a matter of
days or weeks, but rivers have a continuity of existence measured in
thousands of years. I trust that nobody is going to argue that the river
makes any decisions at all?
As you imply above (I think), you have to keep looking (or someone
does, presumably the interpreter) to know whether an object is the
same as or just equal to another (which starts to sound spookily like
the role of the observer in phenomenology or quantum physics).
No, I think you're introducing mysticism here that isn't needed. A bit
like quantum mechanics, really :)
In Python, every object has an identity and a value. If objects X and Y
have the same identity, they are the same object. If X is the object with
id 1234, and Y is the object with id 1234, then both are the same object.
If their ids are different, then they are not.
In CPython, the id is given by the memory location of the object, which
leads to a very intuitive understanding of same: the object with id
1234 is at memory location 1234, and since there can only be one object
at a particular memory location at a time, obviously all objects with id
1234 must be the same object (provided they exist simultaneously).
(To be pedantic, there can't actually be objects [note plural] existing
simultaneously with the same id. There can only be multiple references to
the one object.)
In Python implementations where the id is not a memory address
(IronPython and Jython I think?) the above remains true, even though
there isn't the simple intuitive picture of only one object can be at a
specific memory address. Python guarantees that the id is *something*
which is guaranteed to be unique over the lifetime of every object.
Actually, our intuition about one thing per place at the one time is not
strictly correct. Consider the memory address 1234, which currently has
the value in hex of 0x58. That byte may be the numeric value 88, the
ASCII char X, the set of flags 1011000, or any other thing, depending
on what interpretation we give to it. What a thing is is actually a
more difficult question than it appears at first glance.
[...]
I think the key ingredient is that there's no such thing as side
effect in math.
I don't see that this is relevant. We're not talking about
Re: Testing if an index is in a slice
On Jan 3, 8:53 pm, Bryan Olson fakeaddr...@nowhere.org wrote: If we add a parameter for the length of the list to which the slice is applied, then inslice() is well-defined. Cool! I thought it would easy to write, Heh, I gave up on the example I mentioned above :) but that was hours ago when I knew less about Python slice indexing than I do now. And I thought I new a bunch from writing a virtual slice class. Maybe you could write about what you learned in the docs? I'm leaning towards mmanns' idea that this should be built in. Handling all the cases is remarkably tricky. Even without testing your code, I agree. I suggest that you add this as a feature request to the tracker at http://bugs.python.org/. I hope Raymond Hettinger likes it and adds an islice version :) -- http://mail.python.org/mailman/listinfo/python-list
[issue4815] idle 3.1a1 utf8
Pavel Kosina g...@post.cz added the comment: You can open script made in python 2.x and it stops immediately working after saving, if it is coding-aware. You can have bigger project and use idle for editing config and text files from this project too. It is unfair to change without notification the encodings. Or do you consider IDLE just for beginners for learning? ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Pavel Kosina g...@post.cz added the comment: I forgot about Perhaps IDLE should offer to convert it on opening. That would be nice, too. ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Martin v. Löwis mar...@v.loewis.de added the comment: Here is a patch to provide an explicit message that the file will be converted when the file is opened (also querying what encoding should be converted from), answering the complaint that the conversion is without notice. If you want to edit Python 2.x scripts with IDLE 3, you need to add encoding declarations to the files. For bigger projects, it is reasonable to expect that they do add these declarations. Again, please only report one issue at the time. You chose to make Python source files the topic of this issue, so please don't divert into config or text files. ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Pavel Kosina g...@post.cz added the comment: Sorry, where is the patch? ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Changes by Martin v. Löwis mar...@v.loewis.de: -- keywords: +patch Added file: http://bugs.python.org/file12561/conv.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Changes by Martin v. Löwis mar...@v.loewis.de: -- keywords: +needs review priority: - release blocker ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4796] Decimal to receive from_float method
Changes by Raymond Hettinger rhettin...@users.sourceforge.net: -- assignee: rhettinger - marketdickinson keywords: +needs review -patch Added file: http://bugs.python.org/file12562/decimal2.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4796 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4796] Decimal to receive from_float method
Changes by Raymond Hettinger rhettin...@users.sourceforge.net: Removed file: http://bugs.python.org/file12558/decimal.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4796 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Pavel Kosina g...@post.cz added the comment: OK, I got it. In my opinion it would nice if user can either convert file to utf8 or to do nothing and add new encodings declaration or cancel. Current Cancel gives an Decoding error. If you give an encodings that doesn't exist, it shouldn't destroy IDLE. Hoping its not my mistake, cause I do not have all files from 3.1a - just those from idlelib. ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4796] Decimal to receive from_float method
Mark Dickinson dicki...@gmail.com added the comment:
Instead of the repeated divisions and Inexact tests, how about a direct
approach: n/2**k = (n*5**k)/10**k, so something like:
sign = 0 if copysign(1.0, self) == 1.0 else 1
n, d = abs(self).as_integer_ratio()
k = d.bit_length() - 1
return _dec_from_triple(sign, str(n*5**k), -k)
should work, and would likely be faster too.
I also think the sign of 0 should be preserved: i.e.,
Decimal.from_float(-0.0)
Decimal('-0')
Am still reviewing---more comments to come.
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[issue4816] Patch of itertools.{combinations, permutations} for empty combinations
New submission from Thomas Finley tfin...@gmail.com:
This is a patch for the Python 3.1 build checked out from
http://svn.python.org/projects/python/branches/py3k
The current behavior of itertools.combinations(iterable,r) and
itertools.permutations(iterable,r) is to throw a ValueError if iterable
yields fewer than r items. This changes these functions so the
generator instead yields 0 items.
As for my argument for acceptance, while the original behavior is not a
bug insofar as its implementation was deliberate, I'd argue this is
undesirable on grounds of mathematical consistency and functionality.
In mathematics the choose function is defined as (n choose r)=0 for
rn, so itertools.combinations' behavior is inconsistent with its
obvious combinatorial analogy. (Similar for permutations and the
combinatorial P function.)
For functionality I'll cite my own case as anecdote. In writing
regression tests I wanted to ensure that a group of items obeyed a
certain mutually consistent property between all triples. (Something
akin to the triangle inequality.) So:
all(triangle_respected(*triple) for triple in
itertools.combinations(group, 3))
If len(group)=2, that's fine, since with no triangles there is no
inconsistency, and all(())==True. However, the code failed with a
ValueError when groups were that small. Working around this was fairly
awkward, since I wanted to continue to fail noisily if my
triangle_respected function threw a ValueError, and I wasn't sure at all
that it wouldn't if my items were
The patch modifies Modules/itertoolsmodule.c slightly, changing
combinationsobject_new and permutationsobject_new. (Deleting the error
throwing code, and have one line changes in both structures to handle
the nr case. One could handle this special case more efficiently than
I do by not bothering to allocate certain structures in this case, but I
didn't want to tempt fate.) The patch also changes the appropriate
tests in Lib/test/test_itertools.py .
Obviously, this would break code that depends upon Python throwing
ValueError in the event of the combination or permutation sequence being
empty. However, I hope given that combinations and permutations are a
relative novelty that their behavior in this corner case is not yet
etched in stone.
Sorry if this belongs in a PEP -- it seems quite minor, but I don't
quite have a feel what the threshold is.
--
components: Library (Lib), Tests
files: itertools-empty-combinations.diff
keywords: patch
messages: 78943
nosy: TFinley
severity: normal
status: open
title: Patch of itertools.{combinations,permutations} for empty combinations
type: behavior
versions: Python 3.1
Added file: http://bugs.python.org/file12563/itertools-empty-combinations.diff
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[issue4608] urllib.request.urlopen does not return an iterable object
Jakub Wilk uba...@users.sf.net added the comment: Oops, __next__ is OK. Sorry for the confusion. ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4608 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4817] PyOS_GetLastModificationTime is unused
New submission from Ulrich Eckhardt eckha...@satorlaser.com: This is just to record that the above function is wrongly documented, inconsistently implemented, but fortunately unused, so it can be removed. In addition to the patch attached, there are two files that can be removed: Python/getmtime.c RISCOS/Python/getmtime_riscos.c -- components: Interpreter Core files: python-2.7-eradicate-getmtime.0.patch keywords: patch messages: 78945 nosy: eckhardt severity: normal status: open title: PyOS_GetLastModificationTime is unused type: resource usage versions: Python 2.7 Added file: http://bugs.python.org/file12564/python-2.7-eradicate-getmtime.0.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4817 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4751] Patch for better thread support in hashlib
Changes by ebfe knabberknusperh...@yahoo.de: Removed file: http://bugs.python.org/file12557/md5module_small_locks.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4751 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4796] Decimal to receive from_float method
Mark Dickinson dicki...@gmail.com added the comment: A couple more things: 1. There's a typo 'equilvalent' in the decimal.py part of the patch. 2. Can I suggest using return d._fix(self) instead of return self.plus(d) in create_decimal_from_float. The plus method does two things: rounds to the current context *and* converts -0.0 to 0.0; we only want the first of these. (It's always been a source of mild irritation to me that there's no public method for simply rounding a Decimal to a given context---i.e., a public equivalent of _fix.) -- assignee: marketdickinson - rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4796 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4818] Patch for thread-support in md5module.c
New submission from ebfe knabberknusperh...@yahoo.de: Here is another patch, this time for the fallback-md5-module. I know that situations are rare where openssl is not present but threading is. However they might occur out there and the md5module needed some love anyway: - The MD5 class from the fallback module can now also use threads with 'small locks' - The behaviour regarding unicode data input is now consistent as to what the openssl-driven classes do. - Some code cleanup. I might act on the sha modules as way the next days. sha256.c still accepts 's#'... Also see issue #4751 -- files: md5module_small_locks.diff keywords: patch messages: 78947 nosy: ebfe severity: normal status: open title: Patch for thread-support in md5module.c Added file: http://bugs.python.org/file12565/md5module_small_locks.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4818 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Martin v. Löwis mar...@v.loewis.de added the comment: In my opinion it would nice if user can either convert file to utf8 or to do nothing and add new encodings declaration or cancel. Ypu can still add an encoding declaration after the file got converted. Cancelling is also possible. If you give an encodings that doesn't exist, it shouldn't destroy IDLE. Right. Here is a patch that fixes that. Added file: http://bugs.python.org/file12566/conv.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4815] idle 3.1a1 utf8
Changes by Martin v. Löwis mar...@v.loewis.de: Removed file: http://bugs.python.org/file12561/conv.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4815 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4818] Patch for thread-support in md5module.c
Martin v. Löwis mar...@v.loewis.de added the comment: ebfe, please identify yourself with a real name; please also sign a contributor form. -- nosy: +loewis ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4818 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4812] Junk in the decimals namespace
Mark Dickinson dicki...@gmail.com added the comment: Done (r68191 through r68194). -- status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4812 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4816] Patch of itertools.{combinations, permutations} for empty combinations
Mark Dickinson dicki...@gmail.com added the comment: I agree that the proposed behaviour seems more correct: the collection of all subsets of size 4 of range(3) is perfectly valid and well-defined; it just happens to be empty. I've also encountered this in practice (in code that was enumerating partitions of a list into a fixed number of pieces), but in my case it was easier to work around. I guess the counterargument is that the current ValueError might catch bugs early; I don't know how often this is true in practice. In any case, this is Raymond's call. -- assignee: - rhettinger nosy: +marketdickinson, rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4816 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4751] Patch for better thread support in hashlib
ebfe knabberknusperh...@yahoo.de added the comment:
Haypo, we can probably reduce overhead by defining ENTER_HASHLIB like this:
#define ENTER_HASHLIB(obj) \
if ((obj)-lock) { \
if (!PyThread_acquire_lock((obj)-lock, 0)) { \
Py_BEGIN_ALLOW_THREADS \
PyThread_acquire_lock((obj)-lock, 1); \
Py_END_ALLOW_THREADS \
} \
}
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[issue1717] Get rid of more refercenes to __cmp__
Mark Dickinson dicki...@gmail.com added the comment: [Georg Brandl, on spark.py] This is used by asdl_c.py which generates Python-ast.c -- it should be updated. The only issue here is a single comment, which reads: # GenericASTMatcher. AST nodes must have __getitem__ and __cmp__ Still, I'm reluctant to remove or alter the comment without understanding why it was there in the first place. If someone more familiar with AST stuff can confirm that __cmp__ is definitely no longer needed, I'll remove the mention of it from the comment. Misc/cheatsheet This needs a general overhaul. I'll open a separate issue for this, if that's okay with everyone. Presumably 3.0.1 doesn't need to wait for Misc/cheatsheet to be updated. ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1717 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1717] Get rid of more references to __cmp__
Changes by Martin v. Löwis mar...@v.loewis.de: -- title: Get rid of more refercenes to __cmp__ - Get rid of more references to __cmp__ ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1717 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4580] slicing of memoryviews when itemsize != 1 is wrong
Changes by Martin v. Löwis mar...@v.loewis.de: -- keywords: -needs review ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4580 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4580] slicing of memoryviews when itemsize != 1 is wrong
Changes by Martin v. Löwis mar...@v.loewis.de: -- assignee: - pitrou resolution: - accepted ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4580 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4818] Patch for thread-support in md5module.c
Lukas Lueg knabberknusperh...@yahoo.de added the comment: Sent the form by fax ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4818 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4819] Misc/cheatsheet needs updating
New submission from Mark Dickinson dicki...@gmail.com: Misc/cheatsheet could do with an upgrade, both for the 2.x and 3.x branches. For 3.x, I guess the changes needed are quite extensive. I'm not sure how much needs to be changed or added for 2.x; at a quick glance, the 'with' statement, the 'x if b else y' construction, and the unified try-except-finally are missing. -- assignee: georg.brandl components: Documentation messages: 78955 nosy: georg.brandl, marketdickinson severity: normal status: open title: Misc/cheatsheet needs updating versions: Python 2.7, Python 3.1 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4819 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4753] Faster opcode dispatch on gcc
Antoine Pitrou pit...@free.fr added the comment: I'm not an expert in this kind of optimizations. Could we gain more speed by making the dispatcher table more dense? Python has less than 128 opcodes (len(opcode.opmap) == 113) so they can be squeezed in a smaller table. I naively assume a smaller table increases the amount of cache hits. I don't think so. The end of the current table, which doesn't correspond to any valid opcodes, will not be cached anyway. The upper limit to be considered is the maximum value for a valid opcode, which is 147. Reducing that to 113 may reduce cache pressure, but only by a tiny bit. Of course, only experimentation could tell us for sure :) ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4753 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4806] Function calls taking a generator as star argument can mask TypeErrors in the generator
Hagen Fürstenau hfuerste...@gmx.net added the comment: I'm getting confused about whether it's actually desired behaviour that generators can be star arguments. The error message seems to say it's not: argument after * must be a sequence. The docs seem to agree: If the syntax *expression appears in the function call, expression must evaluate to a sequence. However test_extcall specifically tests function calls with (non-sequence) iterables as star arguments. ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4806 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3638] tkinter.mainloop() is meaningless and crash: remove it
Changes by STINNER Victor victor.stin...@haypocalc.com: Removed file: http://bugs.python.org/file11200/tkinter_remove_mainloop.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue3638 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
