🌐 Mailman 3 February 2008 - Tutor - python.org

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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designing POOP
by bhaaluu April 12, 2008

April 12, 2008

Greetings, POOP: Python Object Oriented Programming/Programmer/Program(s).... I have finished the procedural Python version of the Text Adventure Game. See attached uuencoded zip file which contains tag10.py, data.py and actions.py. [uudecode tag.uue; unzip tag.zip; python tag10.zip] Now I am interested in learning how to DESIGN an object-oriented version of the game in Python. All my Python tutorials show me the mechanics of how to MAKE classes. What I'm interested in is the thought processes and/or guidelines that Tutors employ when they sit down to design a POOP. Can I use the procedural program as a specification? I'd like the input/output and gameplay to be the same. However, I'd like to design the program so it can be expanded in the future. If I'm not mistaken, 'reuse' is a design criteria? My main tutorial is: Programming Python for the Absolute Beginner 2E. Michael Dawson. Boston, MA: Thomson Course Technology, 2006. ISBN-13 978-1-59863-112-8 I also have access to online tutorials. Most of the tutorials I've seen are mainly about how to MAKE a class, ie. the mechanics of POOP. Give a person a fish, feed them for a day. Teach them to fish, and they'll be gone fishing all day. I already have examples of how to make classes. Can you explain how to DESIGN classes. (I see a difference here.) How do you design POOP? What are the guidelines you keep in mind to design "good" POOP? Can an absolute beginner learn to design POOP? 8^D -- b h a a l u u at g m a i l dot c o m "You assist an evil system most effectively by obeying its orders and decrees. An evil system never deserves such allegiance. Allegiance to it means partaking of the evil. A good person will resist an evil system with his or her whole soul." [Mahatma Gandhi]

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read from standard input
by Andrei Petre March 26, 2008

March 26, 2008

Hello, I want to read from the standard input numbers until i reach a certain value or to the end of the "file". What is the simplest, straightforward, pythonic way to do it? a sketch of how i tried to do it: [code] while 1 < 2: x = raw_input() if type(x) != int or x == 11: break else: print x [/code] but don't work. and i'm interest in a general way to read until it is nothing to read. to ilustrate that in C: [code] int x; while( scanf("%d",&x) == 1 && x != 11) printf("%d\n", x); [/code] Thanks!

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Anyone fancy giving me some tips and an expert opinion??
by Damian Archer March 18, 2008

March 18, 2008

I have written what i see as a pretty decent script to resolve this question: Write an improved version of the Chaos program from Chapter 1 that allows a user to input two initial values and the number of iterations and then prints a nicely formatted table showing how the values change over time. For example, if the starting values were .25 and .26 with 10 iterations, the table might look like this: index 0.25 0.26 ---------------------------- 1 0.731250 0.750360 2 0.766441 0.730547 3 0.698135 0.767707 4 0.821896 0.695499 5 0.570894 0.825942 6 0.955399 0.560671 7 0.166187 0.960644 8 0.540418 0.147447 9 0.968629 0.490255 10 0.118509 0.974630 Although it works I am sure I could have gone about this a better way, it probably doesn't fit all the rules of best practice either. Was wondering if anyone would mind having a look and offering a few tips?? # chaos.py # A program to mimic the chaos theory def main(): print "Example of Chaos" # User inputs numbers to compare, z is for the index counter x = input("Enter a number between 1 and 0: ") y = input("Enter a second number between 1 and 0: ") z = 0 # Prints the table borders and titles print '%10s %20s %20s' % ("Index", x, y) print "----------------------------------------------------------" tempx = x tempy = y # Loops calculates 'chaotic behaviour for input numbers for i in range(10): tempx = 3.9 * tempx * (1 - tempx) tempy = 3.9 * tempy * (1 - tempy) z = z + 1 # Print chaotice results into table print '%10s %20s %20s' % (z, tempx, tempy) raw_input("Press any key to exit") main() Thanks!!! And thanks for all the help you've all supplied me with so far, you guys certainly are an extremely valuable resource!!

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Re: [Tutor] Parsing DICOMRT file
by John Fouhy March 15, 2008

March 15, 2008

On 13/12/2007, Bryan Fodness <bryan.fodness(a)gmail.com> wrote: > I am new to doing anything like this. I have looked at > http://www.leadtools.com/SDK/Medical/DICOM/ltdc1.htm and am > not sure how to proceed. I haven't much experience here, but this is how I'd proceed, I think: 1. Start by reading the file. It's binary data (I guess) so there's no point in reading lines.: rawData = open('file.dcm', 'rb').read() 2. Write a function to parse the preamble: def parsePreamble(data): preamble = data[:128] dicm = data[128:132] # you might need to read up on encodings and things to make sure this test is valid if dicm == 'DICM': return preamble, 132 else: raise NotAPreambleException 3. Write functions to parse data elements. The functions are going to try to parse a data element starting at a particular position, and if successful, return the position of the end of the element. def parseDataelement(data, start): # do stuff -- the web page you linked didn't have enough information here return element, pos 4. Parse the whole thing; def parseDICOM(data): elements = [] try: preamble, next = parsePreamble(data) except NotAPreambleException: preamble, next = None, 0 while True: element, next = parseDataElement(data, next) elements.append(element) # you will need some way of breaking out of this loop, either by checking the structure of # element for an end condition, or by parseDataElement raising an exception. return elements # and maybe preamble too if you want it HTH!

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Need help with encoder & decryption keys
by Trey Keown March 3, 2008

March 3, 2008

Hey all, Been away for a while. So, I'm in the process of making a program for encrypting and decrypting strings of text. And I was wondering how it would be possible to perhaps keep keys in a .pyc file, and keep them from being isolated, and messages being intercepted. So... is it possible to decompile things within a .pyc file? This isn't for any serius project, just me attempting to make something to prove that I can do it. Thanks for any help.

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comparison bug in python (or do I not get it?)
by Hans Fangohr March 1, 2008

March 1, 2008

Dear Python folks, here is a sequence of commands (ipython) that lead to a question. See my comments after leading '#': In [1]: 2 in [1,2,3] Out[1]: True #nothing special here, of course 2 is in the list. In [2]: 2 in [1,2,3] == True Out[2]: False #This is somewhat surprising, as one would hope that '2 in [1,2,3]' #evaluates to 'True', and then we expect 'True'=='True' to hold. #However, maybe it is an issue of operator precedence. Let's add parenthesis: In [3]: (2 in [1,2,3]) == True Out[3]: True #Okay, so this does what we expect. #However, if it is an issue of operator precedence, then what is the #operation that is carried out at prompt [2] above? # #Presumably, we work out In [4]: [1,2,3] == True Out[4]: False #which is false. So effectively, The statement at [2] seems to boil down to In [5]: 2 in False --------------------------------------------------------------------------- exceptions.TypeError Traceback (most recent call last) /Volumes/Minmax250a/Users2/fangohr/<console> TypeError: iterable argument required But this throws an error! And so does the full expression (with paranthesis): In [6]: 2 in ([1,2,3] == True) --------------------------------------------------------------------------- exceptions.TypeError Traceback (most recent call last) /Volumes/Minmax250a/Users2/fangohr/<console> TypeError: iterable argument required So what is the story here? In my view, the statement in line [2] should either produce True (as in [3]), or throw an error (as in [6]). Why does [2] return False? Would people agree that this is a bug? Thank you for your time, Hans PS I have tested this with Python 2.4, and Python 2.5 (on debian etch) -- Hans Fangohr School of Engineering Sciences University of Southampton Phone: +44 (0) 238059 8345 Email: fangohr(a)soton.ac.uk http://www.soton.ac.uk/~fangohr

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