🌐 Mailman 3 October 2005 - Python-list - python.org

Re: Scanning a file
by Paul Watson Nov. 1, 2005

Nov. 1, 2005

Steve Holden wrote: >> Since everyone needs this, how about building it in such that files >> which are closed by the runtime, and not user code, are reported or >> queryable? Perhaps a command line switch to either invoke or suppress >> reporting them on exit. >> > This is a rather poor substitute from correct program design and > implementation. It also begs the question of exactly what constitutes a > "file". What about a network socket that the user has run makefile() on? > What about a pipe to another process? This suggestion is rather > ill-defined. > >> Is there any facility for another program to peer into the state of a >> Python program? Would this be a security problem? > > It would indeed be a security problem, and there are enough of those > already without adding more. > > regards > Steve All I am looking for is the runtime to tell me when it is doing things that are outside the language specification and that the developer should have coded. How "ill" will things be when large bodies of code cannot run successfully on a future version of Python or a non-CPython implementation which does not close files. Might as well put file closing on exit into the specification. The runtime knows it is doing it. Please allow the runtime to tell me what it knows it is doing. Thanks.

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Asyncore Loop Question
by John W Nov. 1, 2005

Nov. 1, 2005

Hello, I have a gui application where I am trying to use the asyncore module to gather data from other computers. I am able to connect, but I am getting constant handle_write_event method calls into my application. It is obviously slowing down the gui processing significantly. My understanding is that the handle_write_event and handle_read_event are both edge notifications and I should just get the method call essentially just once. I think the problem is how I have my loop() call configured. All I am trying to do with the code below is to open the socket (that works) and then receive a single handle_write_event method call. Instead, I am getting constantly barraged with them. I have tried several different types of the loop() call (using poll, timeout...) but with no luck. If anyone can explain what I should be doing to get a single handle_write_event call until I actually write something to the socket (which my code is not presently doing yet), I would appreciate Below is some code showing what I am doing: -------------------------------------------------------------- class Connection(asyncore.dispatcher): def __init__ (self, server_name, port_num ): self.message_queue = [] asyncore.dispatcher.__init__(self) self.create_socket( socket.AF_INET, socket.SOCK_STREAM ) self.connect(( server_name, port_num )) def handle_read_event( self ): print "handle_read_event received" def handle_write_event( self ): print "Asking for a write" if len( self.message_queue ) > 0: # Pop the first message off the queue self.send_next_message() class TestApp: def __init__( self, server_name, port_number ): self.nomad = Connection( server_name, port_number ) asyncore.loop() Output ends up being a constant stream of: Asking for a write Asking for a write Asking for a write Asking for a write Asking for a write .... ... ...

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MacOS Extension Carbon.File.FSCatalogInfo file sizes should be UInt64?
by donbro Nov. 1, 2005

Nov. 1, 2005

If my read of the extension source (Mac/Modules/file/_Filemodule.c) is correct, the parameter sizes specified for data and resource file sizes are UInt32 where they should be UInt64. In both OS9 and OSX Carbon, the MacOS File Manager (Files.h) uses UInt64 values for data and resource filesizes. Testing Python 2.3 and 2.4.2 on MacOS 10.3 returns 0L for the file size values and correct values for other elements such as parentDirID: >>> fsRef = FSRef('LICENSE') >>> catinfo, d1, d2, d3 = fsRef.FSGetCatalogInfo(-1L) >>> catinfo.dataPhysicalSize 0 >>> catinfo.parentDirID 2026177 in Files.h, both OS9 and OSX Carbon, the elements are UInt64: struct FSCatalogInfo { [...] UInt64 dataLogicalSize; UInt64 dataPhysicalSize; UInt64 rsrcLogicalSize; UInt64 rsrcPhysicalSize; [...] } in _Filemodule.c the spec looks to be 32 bit: static PyObject *FSCatalogInfo_get_dataLogicalSize(FSCatalogInfoObject *self, void *closure) { return Py_BuildValue("l", self->ob_itself.dataLogicalSize); } I have, perhaps naively, just changed my local copy to use a BuildValue parameter of "L" instead of "l" for each of these get and set methods and this has survived my initial testing: static PyObject *FSCatalogInfo_get_dataLogicalSize(FSCatalogInfoObject *self, void *closure) { return Py_BuildValue("L", self->ob_itself.dataLogicalSize); } But my questions are: Has anyone else seen this? Does this seem like the right fix? There is another routine in _Filemodule.c: FSCatalogInfo_tp_init() that also seems to hold information relevant to parameter size. Should this be changed as well? If this is a bug, what's the best procedure to report this? Sourceforge? This mailing list? I'm porting a MacOS9 application from C++ to python and I expect to be seeing a lot of these python macintosh filesystem extensions in the near future! Thanks for any help Don

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Re: Arguments for button command via Tkinter?
by Ron Adam Oct. 31, 2005

Oct. 31, 2005

Steve Holden wrote: > Francesco Bochicchio wrote: > >> Il Mon, 31 Oct 2005 06:23:12 -0800, dakman(a)gmail.com ha scritto: >> >> >>> And yet the stupidity continues, right after I post this I finnally >>> find an answer in a google search, It appears the way I seen it is to >>> create a class for each button and have it call the method within that. >>> If anyone else has any other ideas please tell. >> >> >> >> This is how I do it: Supposing I have three buttons b1, b2 and b3, and I >> want for each button to call the same callback with, as argument, the >> button itself: >> >> >> def common_callback(button): >> # callback code here >> >> >> class CallIt(objetc): >> def __init__(function, *args ): >> self.function, self.args = function, args >> def __call__(self, *ignore): >> self.function(button, *self.args) >> >> b1['command']= CallIt(common_callback, b1) >> b2['command']= CallIt(common_callback, b2) >> b3['command']= CallIt(common_callback, b3) >> >> This way you need only one class (a sort of custom callable) and >> its instances gets called by Tkinter and in turn calls your >> callback with the proper arguments. >> > I don't see why this is preferable to having the callback as a bound > method of the button instances. What's the advantage here? It looks > opaque and clunky to me ... I'm not sure on the advantage either. I just recently started handling my buttons with button id's. def __init__(self, *args, **kwds): ... b1 = Tk.Button( frame, text=button, command=self.command(button) ) ... The button label is used as the id above, but a number or code could also be used. def command(self, id): """ Assign a command to an item. The id is the value to be returned. """ def do_command(): self.exit(event=id) return do_command In this case it's a dialog button so it calls the exit method which sets self.return to the button id before exiting. Cheers, Ron

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Re: Rename files with numbers
by dudufigueiredo＠gmail.com Oct. 31, 2005

Oct. 31, 2005

Micah, thanks a lot, but my focus is to learn how to acess a folder and rename all files in this folder. Somyhing like this: def renamer(folder, band): folder = #place to act archive = #file to transform rest = archive[3:] print band + " -", rest.capitalize() And than just do this: renamer('C:\My Shared Folder\Rubber Soul', 'The Beatles') And than pyhton alter all files in my folder. Is it possible? I'm a beginer, for now, i just want to let the spaces and apostrophes as they are...

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[Ann] RO package 2005-10-31
by Russell E. Owen Oct. 31, 2005

Oct. 31, 2005

RO package 2005-10-31 is now available from <http://www.astro.washington.edu/rowen/ROPython.html> What is it? A package of python utilities I wrote to support a telescope control interface. RO has a strong emphasis on the Tkinter GUI library, networking, astronomy and cross-platform support (unix, MacOS X and Windows). For more information, follow the link above. Changes include: - RO.DS9 is smarter about finding ds9 and xpa and can now handle byteswapped arrays. - RO.Prefs now can map old pref names to new (allowing one to migrate a preference name). For a full version history see: <http://www.astro.washington.edu/rowen/ROVersionHistory.html> -- Russell

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Python Linked list?
by Simon Roses Femerling Oct. 31, 2005

Oct. 31, 2005

Hi there! I'm looking for a linked list class or lib ? Any suggestions ? Is for a project I'm working on. Sincerely, Simon Roses Femerling

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Recursive generators and backtracking search
by Talin Oct. 31, 2005

Oct. 31, 2005

I've been using generators to implement backtracking search for a while now. Unfortunately, my code is large and complex enough (doing unification on math expressions) that its hard to post a simple example. So I decided to look for a simpler problem that could be used to demonstrate the technique that I am talking about. I noticed that PEP 255 (Simple Generators) refers to an implementation of the "8 Queens" problem in the lib/test directory. Looking at the code, I see that while it does use generators, it doesn't use them recursively. As an alternative, I'd like to present the following implementation. If you compare this one with the one in lib/test/test_generator.py you will agree (I hope) that by using recursive generators to implement backtracking, the resulting code is a little more straightforward and intuitive: # Example of using generators to implement backtracking search. # The example below is an implementation of the classic "N queens" # problem (place N queens on an N x N chessboard so that none are # threatened by the others.) # # Board representation: Since no two queens can be one the same # row, the board is represented as a tuple of N length, where # each element is the column occupied by the queen on that row. def queens( bsize ): # Function to test if a queen is threatened by any previously # placed queen. def threaten( qarray, newpos ): # Now check the diagonals dist = len( qarray ) # Distance between rows for q in qarray: if q == newpos: return True # Same column if q + dist == newpos: return True # diagonal if q - dist == newpos: return True # diagonal dist -= 1 return False def qsearch( qarray = () ): for q in range( 0, bsize ): # Try each position if not threaten( qarray, q ): # If not threatened pos = qarray + ( q, ); # Append to the pos array if len( pos ) >= bsize: # Are we done? yield pos # Yield the answer else: # recursively call new generator for pos in qsearch( pos ): yield pos print "Queens problem for", bsize, "x", bsize, "board." for ans in qsearch(): ` # Print out the board print "+" + "---+" * bsize; for q in ans: print "|" + " |" * q + " Q |" + " |" * (bsize - q - 1) print "+" + "---+" * bsize; print queens( 8 ) Now, you may be wondering what is my point? Well, first, I want to encourage people to think about using Python as a language for complex heuristic search problems. Traditionally, LISP and Prolog have been the language of choices for "AI" type programming, however there is a clear advantage to the readability and maintainability of Python, as well as being much more integrated into modern computing environments (in terms of available interpreters, IDEs, libraries, etc.) Secondly, I want to lobby for additional support in the language and standard libraries for handling such problems. There are a number of fairly obvious language enhancements which would make the above example even simpler - for examle, the idea of being able to return the output of one generator directly from another instead of having to iterate through all of the results and then re-yield them has already been discussed in this forum.

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Re: Problem With Insert with MySQLdb
by Steve Horsley Oct. 31, 2005

Oct. 31, 2005

David Mitchell wrote: > Hello, > > I am a complete beginner with Python. I've managed to get mod_python up and > running with Apache2 and I'm trying to a simple insert into a table in a > MySQL database. > > I'm using the MySQLdb library for connectivity. I can read from the database > no problem, but when I do an insert, the value never gets added to the > database, even though there is no error, and the SQL is fine (I print out > the SQL statement in the function). When I copy and paste the sql from my > browser and insert directly into MySQL, it works fine. > > Here is the function in question: > > def add(req): > db = MySQLdb.connect(host="intranet", user="root", passwd="", > db="intranet") > # create a cursor > cursor = db.cursor() > # execute SQL statement > > sql = "INSERT INTO category (category_name) VALUES ('" + > req.form['category'] + "')" > cursor.execute(sql) > return sql > > > The SQL it is outputting is: > > INSERT INTO category (category_name) VALUES ('Test') > > Am I doing something obviously incorrect here? > > Thanks, > > Dave > Try either executing this first: cursor.execute("set autocommit = 1") or this afterwards: cursor.execute("commit") The idea is that transactions are not committed into the database until you "commit" them - and if you hit problems halfway through a sequence of updates that really shouldn't be left half finished, you can execute "abort" instead (or just close the connection), and none of them will be done. Steve

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Function returns none
by noahlt＠gmail.com Oct. 31, 2005

Oct. 31, 2005

I'm trying to write a website updating script, but when I run the script, my function to search the DOM tree returns None instead of what it should. I have this program: -------- import sys from xml.dom.minidom import parse # search the tree for an element with a particular class def findelement(current, classtofind, topnode = None): if topnode == None: topnode = current # if it's an xml element... if current.nodeType == 1: print current.nodeName, ':', current.getAttribute('class') if current.getAttribute('class') == classtofind: print 'Returning node:', current return current elif current.hasChildNodes(): findelement(current.firstChild, classtofind, topnode) elif current.nextSibling: findelement(current.nextSibling, classtofind, topnode) elif (current.parentNode != topnode) \ and (current.parentNode.nextSibling != None): findelement(current.parentNode.nextSibling, classtofind, topnode) else: print 'Returning None...' return None # others (text, comment, etc) else: if current.nextSibling: findelement(current.nextSibling, classtofind, topnode) elif (current.parentNode != topnode) \ and (current.parentNode.nextSibling != None): findelement(current.parentNode.nextSibling, classtofind, topnode) else: print 'Returning None...' return None # parse the document blog = parse('/home/noah/dev/blog/template.html') # find a post postexample = findelement(blog.documentElement, 'post') print 'Got node: ', postexample ----- My output is this: ----- html : head : title : body : h1 : ul : li : h2 : ol : li : post Returning node: <DOM Element: li at -0x48599c74> Got node: None ----- The function finds the right element fine, and says it will return <DOM Element: li at -0x48599c74>, but the program gets None instead. What's happening here? Any suggestions?

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