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

Re: Why date do not construct from date?
by Lie Ryan June 3, 2009

June 3, 2009

Gabriel Genellina wrote: > En Tue, 02 Jun 2009 03:14:22 -0300, Chris Rebert <clp2(a)rebertia.com> > escribió: > >> On Mon, Jun 1, 2009 at 10:25 PM, Alexandr N Zamaraev >> <tonal(a)promsoft.ru> wrote: > >>>>>> import datetime as dt >>>>>> d = dt.date(2009, 10, 15) >>>>>> dt.date(d) >>> Traceback (most recent call last): >>> File "<stdin>", line 1, in <module> >>> TypeError: function takes exactly 3 arguments (1 given) > >>> Why int form int, str from str, Decumal from Decumal can construct >>> bat date from date not? >> >> Probably because the function signatures would be so different. str(), >> int(), etc *always* take *exactly one* argument -- the object to >> convert. In contrast, date() takes several integers corresponding to >> the year, month, and day. Adding a second signature to it that took >> exactly one argument (of type `date`) and copied it would be >> significantly different from its other signature; in idiomatic Python, >> one would typically make a separate, new function for this drastically >> different signature. > > That doesn't convince me. It's not very consistent along the various > types: int("3ab0",16) is rather different than int(3.2) but they're the > same function... Strictly speaking int("3ab0",16) does not create an int from an int, instead it creates an int from a string. Maybe you want to say int(3) -> 3 ? >> However, the `date` type is immutable, so there's no reason at all to >> try and copy a new instance from an existing one anyway, thus a >> single-argument copy-constructor is completely unnecessary, hence why >> there isn't one. > > Isn't the same for all other examples (int, float, str, Decimal...)? > They're all immutable types, and some have several and rather different > constructor signatures: int(ob), float(ob), and str(ob) are type casting (strictly speaking it is not a type casting, but you get the idea); while date() is a constructor for the date object. Strictly speaking int(ob), float(ob), and str(ob) merely calls the special ob.__int__, ob.__float__, and ob.__str__. These special functions are there to convert the current object into int, float, or str wherever defined. It just happens that calling int.__int__, float.__float__, and str.__str__ just returns themselves. For Decimal, (I think) it is as a symmetry to float since Decimal is intended to be used whenever IEEE 764 behavior does not suit you.

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Re: how to get the path of a module (myself) ?
by Steven D'Aprano June 3, 2009

June 3, 2009

On Tue, 02 Jun 2009 01:46:23 +0200, Stef Mientki wrote: > MRAB wrote: >> Stef Mientki wrote: >>> hello, >>> >>> I've pictures stored in a path relative to my python source code. To >>> get a picture, I need to know what path I'm on in each python module. >>> I thought __file__ would do the job, >>> but apparently I didn't read the documentation carefully enough, >>> because file is the path to the module that called my module. >>> >>> Any ways to get the path of "myself" ? >>> >> I'm not sure what you mean. I just did a quick test. >> >> # File: C:\Quick test\child.py >> print "name is %s" % __name__ >> print "file is %s" % __file__ >> >> # File: C:\Quick test\parent.py >> import child >> >> print "name is %s" % __name__ >> print "file is %s" % __file__ >> >> # Output: >> name is child >> file is C:\Quick test\child.py >> name is __main__ >> file is C:\Quick test\parent.py > Yes, that's what I (and many others) thought, but now put your code in a > file, let's say the file "test.py", and now run this file by : > execfile ( 'test.py' ) In that case, test.py is not a module. It's just a file that by accident has a .py extension, which is read into memory and executed. If you bypass the module mechanism, don't be surprised that you've bypassed the module mechanism :) What are you trying to do? Using execfile is probably not the right solution. -- Steven

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problem with sockets and transferring binary files
by thebiggestbangtheory＠gmail.com June 3, 2009

June 3, 2009

Dear all, I am a python newbie. I am now progressing to writing a network app in python to learn more about it. I have a client and a server in python. The client sends a msg to the server asking it to tar a binary .dbxml file and then send it over to it. The steps are: from the 1. Client sends msg to server 2. Server tars up binary file and Encrypts it using ezpycrypto 3. Server sends it to client 4. Client receives file and decrypts it and untars it Surprisingly, the sha1 hash of the encrypted data before it is sent from server is different from the encrypted file data received by the client. I post some code below to provide more info about what I am doing. [code] #client after sending initial msg #get server replywhich sends back the .dbxml file myHost = '127.0.0.1' myPort = 20001 s1 = socket(AF_INET, SOCK_STREAM) # create a TCP socket s1.bind((myHost, myPort)) # bind it to the server port s1.listen(1) # allow 1 simultaneous # pending connections connection, address = s1.accept() # connection is a new socket while 1: data = connection.recv(10000000) # receive up to 10000000 bytes if data: info=decryptfile(data) #we have recieved a compressed .tar.gz file #write out info to a file buf = open(currentpath+'received-container.tar.gz', 'w') buf.write(info) buf.close() #testing code: must be removed os.system('sudo sha1sum '+currentpath+'received-xml- container.tar.gz') #uncompress os.system('sudo tar -xvzf '+currentpath+'received-xml- container.tar.gz') [/code] [code] #the server after receiving the msg from client #dump the binary file os.system('sudo cp '+'/'+path+'1.binary '+currentpath +'1.binary') #compress the file os.system('sudo tar -cvzf '+currentpath+'1.bin.tar.gz '+currentpath+'1.binary') #encrypt the file specified in command line cipher=encryptfile(secretkey, currentpath+'1.bin.tar.gz') #send it over to sender send_to_sender(cipher, senderaddress) #testing code: needs to be removed buf = open(currentpath+'cipher', 'w') buf.write(cipher) buf.close() os.system('sudo sha1sum '+currentpath+'cipher') [/code] [code] #function code def send_to_sender(cipher, servername): PORT = 20001 BUFF = 10000000 clientSocket = socket(AF_INET, SOCK_STREAM) HOST = servername ADDR = (HOST, PORT) clientSocket.connect(ADDR) clientSocket.send(cipher) clientSocket.close() [/code] What I see at the client side is 7105b60d3167f2424d9e2806c49cca86c00577ba received-container.tar.gz gzip: stdin: unexpected end of file tar: Unexpected EOF in archive tar: Unexpected EOF in archive tar: Error is not recoverable: exiting now da39a3ee5e6b4b0d3255bfef95601890afd80709 received-container.tar.gz gzip: stdin: unexpected end of file tar: Child returned status 1 tar: Error exit delayed from previous errors It seems two file pieces are received! but why? The buffer size is big enough to accept the whole thing in one go. The binary file is about 460K in size. Any pointers, comments will be greatly appreciated :-). Thanks

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Seach for encrypted socket wrapper
by Hans Müller June 3, 2009

June 3, 2009

Hello experts, I'm looking for secure way to pass messages from a python program to a c-library in both ways. This scenario is given: display client Calculation module in COBOL (yes, big, old but it works well) (python, wxpython) <- Network connection -> C-Lib beeing called from COBOL to communicaty with display client The network connection should be encrypted. And fail save. Has someone an idea what to use ? I have had a short look on xml rpc which can run over a https server but this seems quite fat. Better ideas ?! Importand is also that the C-Lib on the cobol side should be coded as simple as possible. Platforms: Windows, *ix Thanks a lot. Hans

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Re: Missing codecs in Python 3.0
by Carl Banks June 3, 2009

June 3, 2009

On Jun 2, 7:35 pm, Chris Rebert <c...(a)rebertia.com> wrote: > On Tue, Jun 2, 2009 at 7:15 PM, samwyse <samw...(a)gmail.com> wrote: > > I have a Python 2.6 program (a code generator, actually) that tries > > several methods of compressing a string and chooses the most compact. > > It then writes out something like this: > > { encoding='bz2_codec', data = '...'} > > > I'm having two problems converting this to Py3. First is the absence > > of the bz2_codec, among others. It was very convenient for my program > > to delay selection of the decoding method until run-time and then have > > an easy way to load the appropriate code. Is this gone forever from > > the standard libraries? > > That appears to be the case. "bz2" is not listed onhttp://docs.python.org/3.0/library/codecs.html, but it is listed on > the counterpart 2.6 doc page. > You can always use the `bz2` module instead. Or write your own > encoder/decoder for bz2 and register it with the `codecs` module. IIRC, they decided the codecs would only be used for bytes<->unicode encodings in Python 3.0 (which was their intended use all along), moving other mappings (like bz2) elsewhere. Not sure where they all went, though. It was convenient, admittedly, but also confusing to throw all the other codecs in with Unicode codecs. Carl Banks

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Re: how to find the last decorator of a chain
by aahz＠pythoncraft.com June 3, 2009

June 3, 2009

In article <mailman.939.1243725387.8015.python-list(a)python.org>, Gabriel <gabriel(a)opensuse.org> wrote: > >I have something like this: > >@render(format="a") >@render(format="b") >@.... >def view(format, data): > return data > >Each render will do something with 'data' if format match, and nothing >if not. > >But if there is no more renders to eval, the last one is the default, >and must run even if the format doesn't match. My inclination would be to make this explicit with something like this: def make_render(func, format_list): def tmp(format, data): for f in format_list: if MATCH(format, f): render(data) break else: render(data) return tmp def view(format, data): return data view = make_render(view, ['a', 'b']) IOW, just because we have decorators doesn't mean that they're the best solution for all function-wrapping problems. -- Aahz (aahz(a)pythoncraft.com) <*> http://www.pythoncraft.com/ my-python-code-runs-5x-faster-this-month-thanks-to-dumping-$2K- on-a-new-machine-ly y'rs - tim

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Re: "Exploding" (**myvariable) a dict with unicode keys
by Samuel Wan June 3, 2009

June 3, 2009

I started using python last week and ran into exceptions thrown when unicode dictionary keys are exploded into function arguments. In my case, decoded json dictionaries did not work as function arguments. There was a thread from Oct 2008 (http://www.gossamer-threads.com/lists/python/python/684379) about the same problem. Here is my workaround: ------------------ start code --------------- def safe_dict(d): """Recursively clone json structure with UTF-8 dictionary keys""" if isinstance(d, dict): return dict([(k.encode('utf-8'), safe_dict(v)) for k,v in d.iteritems()]) elif isinstance(d, list): return [safe_dict(x) for x in d] else: return d #Example foo = { 'a':1, 'b':{'b1':2, 'b2':3}, 'c':[ 4, {'D1':2, 'D2':3}, ] } #generate and re-parse json to simulate dictionary with unicode keys dictionary = json.loads(json.dumps(foo)) # shows unicode keys, like u"a" print dictionary # shows utf8 keys, like "a" converted_dictionary = safe_dict(dictionary) fun(**converted_dictionary) ------------------ end code --------------- I really like python! Hope this contributes to the thread. -Sam On Oct 3, 1:57 pm, Peter Otten <__pete...(a)web.de> wrote: > "Martin v. Löwis" wrote: > > Devin wrote: > >> So Python can have unicode variable names but you can't > >> "explode" (**myvariable) a dict with unicode keys? WTF? > > > That works fine for me. > > The OP probably means > > >>> def f(a=1): return a > ... > >>> f(**{"a": 42}) > 42 > >>> f(**{u"a": 42}) > > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: f() keywords must be strings > > Peter Yes, that's exactly what I mean.

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Using C++ and ctypes together: a vast conspiracy? ;)
by Joseph Garvin June 3, 2009

June 3, 2009

So I was curious whether it's possible to use the ctypes module with C++ and if so how difficult it is. I figure in principal it's possible if ctypes knows about each compiler's name mangling scheme. So I searched for "ctypes c++" on Google. The third link will be "Using ctypes to Wrap C++ Libraries". If you follow the link, it's broken. If you view the cache of the link, it's someone pointing to another blog, retrograde-orbit.blogspot.com, saying they discovered a way to do it easily. If you follow that link, you get taken a page does not exist error. Clearly there's some way to use ctypes with C++ and there's a vast conspiracy preventing it from reaching the masses ;) What's even stranger is that this link, despite being broken, has seemingly been near the top of google's results for these terms for a couple weeks (that's when I last tried), as if there were some underground group of rebels trying to hint the truth to us... ;) More seriously -- how difficult is it to use ctypes instead of saying, boost::python, and why isn't this in a FAQ somewhere? ;)

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Re: how to get the path of a module (myself) ?
by Steven D'Aprano June 3, 2009

June 3, 2009

On Tue, 02 Jun 2009 02:55:13 +0200, Stef Mientki wrote: >> What are you trying to do? Using execfile is probably not the right >> solution. >> >> > Maybe you're right, and it's not the best solution for my problem. I've > written a program, that contains many files, both python files and data > files, > and I would like to distribute the program. For Linux, I'll just bundle > the files in a zip-file, but for windows I want to make a one button > installer, and the files generated by Py2Exe, don't work at all. Define "don't work at all". > Through this discussion, I discovered another problem, because __file__ > isn't the current file, I can't run 1 module(file) from another module > (file) . ... It sounds like you are trying to fight Python's module system instead of working with it. In Python programs, you don't "run" other modules, you import them, then call functions inside the module. You treat the modules you write exactly the same as standard library modules. As a general rule, you would never say: execfile('/usr/lib/python2.5/os.py') Instead you would say: import os os.some_function() The same rule applies for your modules. As a general rule, NEVER say: execfile('mymodule.py') instead do: import mymodule mymodule.some_function() mymodule.another_function() (There are exceptions, but if you need to ask what they are, you're not ready to learn them! *wink*) > The structure of my files is something like this: > > Base_Path > Main_Program_Path > Main_Program_1.py > Main_Program_2.py > Brick_Path > Brick_1.py > Brick_2.py > Support_Libraries > Support_Library_1.py > Support_Library_2.py > Sounds_Path > Sound_1.wav > Sound_2.wav > Picture_Path > Picture_1.png > Picture_2.bmp Are these packages? Or just random folders with random files in them? > The Main_Programs, should be able to "run/launch" other Main_Programs > and Support_Libraries, > in several ways (wait / nowait, fetch output or not, ... ). So each > Support_Libraries will have a "main-section". Sounds like a horribly fragile, complicated and complex way of doing things. > Everything is highly > dynamical, just dumping a new py-file in the Brick_Path, will make the > py-files available ( i.e. directly visible and usable to the user) in > all Main_Programs. Sounds like you're trying to implement plugins. For that, __import__() is your friend. execfile() is *not* your friend -- you might think it is, but don't listen to it. It's like one of those guys who calls you "buddy" and talks you into doing things that you regret the next day. Trust me, use execfile() and you'll end up waking up naked in an alleyway in Vegas married to someone called Lula-Mae, with no memory of the last three days and a tattoo of Paris Hilton on your butt. > Distributing the files through Py2Exe doesn't work at all. So I was > thinking of a hack: As soon as you start thinking of using a hack in production code, go take a cold shower and lie down until the urge goes away. > Any suggestions ? Have you tried to find out why Py2Exe is broken and fix that? -- Steven

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py2app and OpenGL, "No module named util" in ctypes
by trhaynes June 2, 2009

June 2, 2009

I'm trying to use py2app to package an OpenGL app, so first I tried to build the example here http://svn.pythonmac.org/py2app/py2app/trunk/examples/PyOpenGL/ and I get the error: > File "/opt/local/lib/python2.5/site-packages/PyOpenGL-3.0.0c1-py2.5.egg/OpenGL/platform/darwin.py", line 24, in <module> > import ctypes, ctypes.util >ImportError: No module named util >2009-05-28 13:55:06.819 lesson5[19965:10b] lesson5 Error >2009-05-28 13:55:06.821 lesson5[19965:10b] lesson5 Error >An unexpected error has occurred during execution of the main script > >ImportError: No module named util But when I open up my python interactive interpreter and "import ctypes.util", it works fine (using lesson5.app/Contents/MacOS/python, too). Thanks for the help. -tom

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