Mailman 3 November 2010 - Tutor

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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Running .py files in shell
by Kevin Rapley Sept. 22, 2011

Sept. 22, 2011

Hello all, I am new to programming and have opted to learn Python as I hear it is a good first language. I am currently going through the exercises in 'How to Think Like a Computer Scientist: Learning with Python 2nd Edition'. I am running Mac OSX v10.6.4 Snow Leopard I am running Python 2.6.1 I have a couple of questions: 1. How do I execute .py files in the command line shell? I have my files in /Users/Kevin/python-exercises/ and am opening python in shell from that directory 2. How do I install GASP which is referenced in chapter 4? The instructions in this book are not complete. I have researched and found a reference on Stack Overflow which is contributed to by GASP programmers http://stackoverflow.com/questions/1024862/how-do-i-install-gasp-for-python… I have MacPorts installed and have attempted to install PyObjC, which is referenced as a prerequisite to PyGame and GASP. I get the following error when attempting to install PyObjC: sudo port install py-pyobjc Password: ---> Computing dependencies for py-pyobjc ---> Fetching py-pyobjc Error: Target org.macports.fetch returned: PyObjC 1.4 is for Mac OS X 10.4 and lower. On 10.5, use py-pyobjc2 instead. Log for py-pyobjc is at: /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_ports_python_py-pyobjc/main.log Error: Status 1 encountered during processing. It says to use py-objc2 instead, so I do so and get this error: sudo port install py-pyobjc2 Error: Target org.macports.activate returned: Image error: /opt/local/lib/python2.4/site-packages/modulegraph/__init__.py is being used by the active py-modulegraph port. Please deactivate this port first, or use 'port -f activate py-modulegraph-devel' to force the activation. Log for py-modulegraph-devel is at: /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_ports_python_py-modulegraph-devel/main.log Error: The following dependencies failed to build: py-py2app-devel py-modulegraph-devel Error: Status 1 encountered during processing. To report a bug, see <http://guide.macports.org/#project.tickets> I attempted to correct the issue by entering the following: port -f activate py-modulegraph-devel But it returned this error: Warning: Failed to open Portfile from registry for py-modulegraph-devel @0.7.2_0 ---> Activating py-modulegraph-devel Error: port activate failed: sqlite error: attempt to write a readonly database (8) This is as far as I have got with resolving this issue so far. All help and guidance will be greatly appreciated. Kevin Rapley

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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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2to3 conversion
by Zubin Mithra July 1, 2011

July 1, 2011

Hey everyone, I was running 2to3 on a particular file and I got the following traceback( http://paste.pocoo.org/show/223468/). The file which I was attempting to convert can be viewed here( http://paste.pocoo.org/show/223469/). Any pointers on what needs to be done? Thanks in advance, Zubin

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sftp get single file
by Matt Herzog June 22, 2011

June 22, 2011

Hello All. I need to use paramiko to sftp get a single file from a remote server. The remote file's base name will be today's date (%Y%m%d) dot tab. I need help joining the today with the .tab extension. Do I need globbing? example: 20090716.tab #!/usr/bin/env python import paramiko import glob import os import time hostname = 'sftp.booboo.com' port = 22 username = 'booboo' password = '07N4219?' # glob_pattern='*.tab' today = time.strftime("%Y%m%d") remotepath = today.tab localpath = '/home/data/text' if __name__ == "__main__": t = paramiko.Transport((hostname, port)) t.connect(username=username, password=password) sftp = paramiko.SFTPClient.from_transport(t) sftp.get(remotepath, localpath) t.close() -- I fear you speak upon the rack, Where men enforced do speak anything. - William Shakespeare

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Plotting a Linear Equation
by Corey Richardson April 21, 2011

April 21, 2011

Hello tutors. Probably the wrong mailing list, but someone might know. I want to use matplotlib (or similar) to plot an equation in slope-intercept (y=mx+b) or standard form (Ax + By = C). As far as I've read and tested, you can only plot with a series of points. I could make two points out of those manually, but I was wondering if anyone knew of an easier way. Thanks.

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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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Pyserial and invalid handle
by John Smith Dec. 3, 2010

Dec. 3, 2010

Can anybody tell me why the handle below is invalid? I'm running Win7. TIA, John Python 2.7 (r27:82525, Jul 4 2010, 07:43:08) [MSC v.1500 64 bit (AMD64)] on win32 Type "copyright", "credits" or "license()" for more information. >>> import serial >>> ser = serial.Serial('com1', timeout = 5) >>> x = ser.read() Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> x = ser.read() File "E:\Python27\lib\site-packages\serial\serialwin32.py", line 236, in read raise SerialException("ReadFile failed (%s)" % ctypes.WinError()) SerialException: ReadFile failed ([Error 6] The handle is invalid.) >>>

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How to handle exceptions raised inside a function?
by Richard D. Moores Dec. 2, 2010

Dec. 2, 2010

Please take a look at 2 functions I just wrote to calculate the harmonic and geometric means of lists of positive numbers: <http://tutoree7.pastebin.com/VhUnZcma>. Both Hlist and Glist must contain only positive numbers, so I really need to test for this inside each function. But is there a good way to do this? What should the functions return should a non-positive number be detected? Is there a conventional Pythonic way to do this? Thanks, Dick Moores

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A regular expression problem
by Josep M. Fontana Dec. 1, 2010

Dec. 1, 2010

I'm trying to use regular expressions to extract strings that match certain patterns in a collection of texts. Basically these texts are edited versions of medieval manuscripts that use certain symbols to mark information that is useful for filologists. I'm interested in isolating words that have some non alpha-numeric symbol attached to the beginning or the end of the word or inserted in them. Here are some examples: '¿de' ,'«orden', '§Don', '·II·', 'que·l', 'Rey»' I'm using some modules from a package called NLTK but I think my problem is related to some misunderstanding of how regular expressions work. Here's what I do. This was just a first attempt to get strings starting with a non alpha-numeric symbol. If this had worked, I would have continued to build the regular expression to get words with non alpha-numeric symbols in the middle and in the end. Alas, even this first attempt didn't work. --------- with open('output_tokens.txt', 'a') as out_tokens: with open('text.txt', 'r') as in_tokens: t = RegexpTokenizer('[^a-zA-Z\s0-9]+\w+\S') output = t.tokenize(in_tokens.read()) for item in output: out_tokens.write(" %s" % (item)) -------- What puzzles me is that I get some results that don't make much sense given the regular expression. Here's some excerpt from the text I'm processing: --------------- "<filename=B-05-Libro_Oersino__14-214-2.txt> %Pág. 87 &L-[LIBRO VII. DE OÉRSINO]&L+ &// §Comeza el ·VII· libro, que es de Oérsino las bístias. &// §Canto Félix ha tomado prenda del phisoloffo, el […] ·II· hómnes, e ellos" ---------------- Here's the relevant part of the output file ('output_tokens.txt'): ---------- " <filename= -05- _Oersino__14- -2. %Pág. &L- [LLIBRO ÉRSINO] &L+ §Comenza ·VII· ístias. §Canto élix ·II· ómnes" ----------- If you notice, there are some words that have an accented character that get treated in a strange way: all the characters that don't have a tilde get deleted and the accented character behaves as if it were a non alpha-numeric symbol. What is going on? What am I doing wrong? Josep M.

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