🌐 Mailman 3 November 2008 - Tutor - python.org

Wave module
by Alex Krycek Feb. 12, 2015

Feb. 12, 2015

Hello, I'm trying to join two .wav files with the wave module. But when I try to use wave.open(filename, "rb") I receive the following error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "F:\PortablePython1.0\lib\wave.py", line 483, in open return Wave_read(f) File "F:\PortablePython1.0\lib\wave.py", line 162, in __init__ self.initfp(f) File "F:\PortablePython1.0\lib\wave.py", line 143, in initfp self._read_fmt_chunk(chunk) File "F:\PortablePython1.0\lib\wave.py", line 264, in _read_fmt_chunk raise Error, 'unknown format: %r' % (wFormatTag,) wave.Error: unknown format: 85 I read somewhere that there are various wave formats, only some supported by Python. Is this true? If so, is there any way I can convert my wave files into a supported kind? Thanks!

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Send binary/hex data to a TCP socket
by Tod Haren July 19, 2011

July 19, 2011

I need to send a server at the other end of a socket a 36 byte "frame", where each byte represents a specific field in the custom data structure. (If there are any Ham operators reading this, I'm talking about the AGW Packet Engine) The documentation for the server says to initialize each field to a binary zero(0x00). How do I get a binary zero in Python? The next step is to send this all to the server and subsequently receive a similarly formated frame. A very basic frame looks something like this(modified from documentation): |00 00 00 00 4D 00 00 00 00 00 00 00 00 00 00 00 |....M........... |00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................ |00 00 00 00 |.... My problem is that hex(0) return '0x0' and hex(ord('M')) returns '0x4d'. If I concatonate these all together then the socket receives 109 bytes instead of 36. The documentation examples are in C++, so they are little help to me. The examples make use of the MoveMemory function for building the frames, but I'm clueless what that does. Pseudo code for the frame above: l = [] for i in xrange(36): l.append(hex(0)) l[4]=hex(ord('M')) d='' d=d.join(l) #I need some other data type to send besides a string! sock.send(d) #send the 36 bytes to the socket Any pointers or references would be greatly appreciated.

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cx_Oracle help
by Greg Lindstrom Jan. 6, 2011

Jan. 6, 2011

Hello, I'm trying to help out a friend and am stumped. Can you help me out? Thanks, --greg - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - I will briefly explain the problem I am facing. I am using Oracle 9.2, Python 2.5 and I installed cx_Oracle- 4.3.1-win32-9i-py25 in Python. From python I tried following : >>> import cx_Oracle >>> myDsn = cx_Oracle.makedsn('ISCN47',1521,'AUBDBS01') >>> CONN = cx_Oracle.connect(myusr, mypwd, myDsn) Traceback (most recent call last): File "<pyshell#4>", line 1, in <module> conn = cx_Oracle.Connection('scott','tiger',myDsn) RuntimeError: Unable to acquire Oracle environment handle I have set the below environment variables too NLS_LANG: <snip>.WE8MSWIN1252 ORACLE_HOME: D:\Tools\oracle\ora92 ORACLE_SID: AUBDBS01 PYTHON_HOME: d:\Utility\Python25 PYTHONPATH: %PYTHON_HOME%\lib;%PYTHON_HOME%\DLLs;%PYTHON_HOME%\Lib\site-packages;%ORACLE_HOME%\bin LD_LIBRARY_PATH: %LD_LIBRARY_PATH%;D:\Tools\oracle\ora92\lib Not getting any idea where I am wrong? Regards, Kishore

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Tracking time
by Michael Key Jan. 6, 2010

Jan. 6, 2010

I am trying to develop a project tracking program that would allow you to track hours and minutes spent on several different projects and store he data in a database for printing. Any help would be appreciated. Mike

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Learning Python
by Fred P Dec. 13, 2009

Dec. 13, 2009

Hey Everyone, I am completely new at python, but not new to programming or scripting. I have a couple of years of LUA scripting experience, about a year of C++ classes, and used to be very efficient at c-shell scripting in unix. My question for you guys: 1) How do I get Started? 2) Recommend any specific Books? 3) Any online tutors/ forums that would benefit a newbie 4) Any online classes that teach python? I have taken online c++ courses, and found them helpful. I was hoping to find something for python. My main objective is to write scripts for the following type of applications File management, file copies/syncs/ compares Text manipulation - like parsing text files to replace or augment specific values Integration into current applications to write redundant routines and maybe some day plugins I am not even sure what else, but I do know that every time i think of something that we need at work, other people say, "That would be a good task for a python script" and I would eventually like to be able to do something about that. Thanks Fred

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cx_oracle module problems
by jeremiah July 7, 2009

July 7, 2009

I've downloaded the cx_oracle source module for python, howerver every time i try to build it, it keeps on failing. I've been unable to find a port for Ubuntu. Is there one? Anyone know how to get this properly installed? # sudo python setup.py install Traceback (most recent call last): File "setup.py", line 36, in <module> oracleHome = os.environ["ORACLE_HOME"] File "/usr/lib/python2.5/UserDict.py", line 22, in __getitem__ raise KeyError(key) KeyError: 'ORACLE_HOME' Link: http://prdownloads.sourceforge.net/cx-oracle/cx_Oracle-4.2.tar.gz?download Thanks, JJ Disclaimer: The information contained in this transmission, including any attachments, may contain confidential information of Panasonic Avionics Corporation. This transmission is intended only for the use of the addressee(s) listed above. Unauthorized review, dissemination or other use of the information contained in this transmission is strictly prohibited. If you have received this transmission in error or have reason to believe you are not authorized to receive it, please notify the sender by return email and promptly delete the transmission.

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Python and Abaqus
by iSinhCanon Jan. 13, 2009

Jan. 13, 2009

It would be simply if you can use Python to explorer your file .odb for yours databases for exemples: displacements and stresses at node etc... I have a lot of exemples by using Python for file .odb, if you want i can send it to you. Sinh. Hello folks, This is something that must have been asked several times. I want to post process data obtained after running a FEM in ABAQUS. The requested results are usually printed to the .dat file or .rpt file. I would like to learn how to extract the information that I need (i.e. displacements and stresses at the nodes) from this file using Python. The fact is that I am kind of new at ABAQUS and have zero knowledge about Python. Therefore, any help with websites, examples, tutorials, etc. would be appreciated. Thank you! Andres

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Help Optimise Code
by Richard Lovely Dec. 4, 2008

Dec. 4, 2008

I'm pretty new to code optimisation, so I thought I'd ask you all for advice. I'm making an iterative prime number generator. This is what I've got so far: Code: Select all import math, array def count2(start_at=0): 'Yield every third integer, beginning with start_at' # this has been tested as faster than using itertools.count while True: yield start_at start_at += 2 def iprimes(): 'generate an endless sequence of prime numbers' yield 2 yield 3 yield 5 sqrt = math.sqrt knownPrimes = array.array("L",(3,5)) # 'L' for unsigned long - not tested if using a smaller type is faster for x in count2(7): sqrtX = sqrt(x) # take extra function calls out of the inner loop for p in knownPrimes): test = (not x % p) and -1 or p > sqrtX if test == -1: # (not x % p) == true break elif test: # (p > sqrtX) == true yield x knownPrimes.append(x) break I've tried a the sieve of erath-whatever as in test_generator, implemented using itertools functions, but it hit max recusion depth somewhere before 1000 primes, and I'm after millions of primes. I'm not particularly bothered about startup overheads, just the loops. Quick thought: would the following work (I'm on a public computer without python, so can't test): Code: Select all def iprimes(): 'generate an endless sequence of prime numbers' yield 2 yield 3 yield 5 sqrt = math.sqrt knownPrimes = array.array("L",(3,5)) # 'L' for unsigned long - not tested if using a smaller type is faster for x in count2(7): sqrtX = sqrt(x) # take extra function calls out of the inner loop for test in ((not x % p) and -1 or p > sqrtX for p in knownPrimes)): # a generator _should_ be faster... if test == -1: # (not x % p) == true break elif test: # (p > sqrtX) == true yield x knownPrimes.append(x) break Please don't suggest changing languages. I like python. Although if you want to write an extension for me, and provide the source and a makefile, please feel free. I have a MinGW install that's doing nothing. (Just kidding - almost.) This is NOT homework. -- Richard "Roadie Rich" Lovely, part of the JNP|UK Famile www.theJNP.com

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Re: [Tutor] attribute of built-in type
by Kent Johnson Dec. 1, 2008

Dec. 1, 2008

On Sat, Nov 29, 2008 at 5:09 PM, spir <denis.spir(a)free.fr> wrote: > Kent Johnson a écrit : >> On Fri, Nov 28, 2008 at 6:01 PM, spir <denis.spir(a)free.fr> wrote: >>> Kent Johnson a écrit : >> OK, functions (and methods, which are also functions, both of which >> are instances of some builtin type), classes (which are instances of >> type or classobj) and modules all have __name__ attributes. > > You're right, actually, as I was studying a bit how /some/ built-in types > work, and they all had a __name__, I had a wrong impression about that > attribute. > >>> Anyway, do you have an idea how to let custom objects inherit such >>> attributes (*)? If they were of a custom type, one would just do it with >>> inheritance (multiple, if needed). Now, this does not seem to work with >>> buil-tins -- or I was unable to find the proper way. >> >> I don't understand this paragraph. When you say "custom objects" do >> you mean classes or instances? Custom classes do have __name__ >> attributes; instances in general do not, other than the special cases >> mentioned above. >> >> I *think* what you want is to be able to say something like >> class Foo(object): pass >> myFoo = Foo() >> and then have >> foo.__name__ == 'myFoo' > > Exactly, "custom objects" was a shortcut for "objects that are instances of > custom types". > >> Is that right? If so, first recognize that the object can be assigned >> to many names: >> foo = bar = baz = Foo() >> so what you are asking is not well defined. > > Right. I just need the first one. The object's birthname ;-) ; whatever it > may be in case of "sequential naming", like in your example (which can > happen in my case). > >> Second, search on comp.lang.python for some ideas, this request comes >> up there from time to time. >> >> Third, how about passing the name to the constructor, or assigning the >> attribute yourself? >> myFoo = Foo('myFoo') >> or >> myFoo = Foo() >> myFoo.__name__ = 'myFoo' >> Yes, you have to type the name more than once... > > Actually, it is not an big issue. There are workarounds, anyway (such as > exploring the current scope's dict /after/ object creation, and assigning > its name back to an attribute -- this can also be automatised for numerous > objects). > Still, it would help & spare time & energy... This is also for me (and > hopefully other readers) an opportunity to explore corners of the python > universe ;-) > >> AFAIK Python does not have any hook to modify assignment which I think >> is what you want. You might be able to do something like this with the >> ast module in Python 2.6. You would have to load the code for a >> module, compile it to the AST, modify the AST and compile it to code. >> Some examples of this: >> http://code.activestate.com/recipes/533145/ >> http://pyside.blogspot.com/2008/03/ast-compilation-from-python.html >> >> http://lucumr.pocoo.org/cogitations/2008/03/30/high-level-ast-module-for-py… >> >> I know you explained before but I still don't understand *why* you >> want to do this... > > First, this problem occurs while I'm trying to use code of an external > module for a project of mine. My case is probably specific, otherwise this > issue would have been adressed long ago. > These objects are kinds of "models" -- they control the generation of other > objects -- but they are not classes, and can't be. As a consequence, the > generated objects do not know what they actually are. They have a type, of > course, but this type is general and not related to the real nature of the > objects that share it. It would be a first step if the generators first > would themselves know 'who' they are; then they would be able to pass this > information to their respective "chidren". This would be a very small and > harmful hack in the module's code (which is nice to study, not only for its > organisation, also because it is not built upon further modules). Do you know that you can probably just assign a __name__ attribute to the objects? Or name, or whatever you like? In [13]: class Foo(object): pass ....: In [14]: f=Foo() In [15]: f.name --------------------------------------------------------------------------- AttributeError Traceback (most recent call last) /Users/kent/<ipython console> in <module>() AttributeError: 'Foo' object has no attribute 'name' In [16]: f.name = 'f' In [17]: f.name Out[17]: 'f' This will work for custom objects that do not have a __slots__ attribute. Perhaps you could wrap the creation of the objects in a function that gives them a name? >>> (*) The point is that they can't be written by hand. How would you do it >>> e.g. that an attribute automatically holds the objects own name? You can >>> play with the namespace's dict, but it's the same thing. (It's like >>> inheriting for instance an integer's behaviour: yes, you can rewrite it >>> from >>> scratch.) >>> class myInt(int): works >>> class myFunc(function): works not >>> TypeError: Error when calling the metaclass bases >>> type 'function' is not an acceptable base type >> >> I don't understand your point here. How would creating your own >> function class help? > > It is an illustration of what i'm trying to do: let a class inherit from > 'function' so that its instances get a __name__. This wouldn't be a harmful > overload I guess, as these objects have a __call__ method anyway (the reason > why I chose 'function'). I doubt this would do what you want. AFAICT the function name is assigned by the compiler, not by the function constructor. (That is a bit of oversimplification but close enough. I think the compiler creates a code object, passing its name to the constructor; when a function object is wrapped around the code object, it pulls its name from the code object.) >> Kent PS Please use Reply All to reply to the list. > > Thank you for your attention and help, > Denis > > >

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Reading gzip files
by Dinesh B Vadhia Nov. 30, 2008

Nov. 30, 2008

I'm reading gzip files and writing the content out to a text file line by line. The code is simply: import gzip list_zipfiles = dircache.listdir(zipfolder) writefile = "out_file.txt" fw = open(writefile, 'w') for ziparchive in list_zipfiles: zfile = gzip.GzipFile(zipfolder + ziparchive, "r") for line in zfile: fw.write(line) zfile.close() fw.close() The Traceback is: Traceback (most recent call last): File "....py", line 47, in <module> for line in zfile: File "C:\Python25\lib\gzip.py", line 444, in next line = self.readline() File "C:\Python25\lib\gzip.py", line 399, in readline c = self.read(readsize) File "C:\Python25\lib\gzip.py", line 227, in read self._read(readsize) File "C:\Python25\lib\gzip.py", line 275, in _read self._read_eof() File "C:\Python25\lib\gzip.py", line 311, in _read_eof raise IOError, "CRC check failed" IOError: CRC check failed I've checked the Python docs and online but cannot find a solution to the problem. Thanks. Dinesh

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