🌐 Mailman 3 March 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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help with slice
by washakie April 2, 2008

April 2, 2008

Could someone please explain 'slices' also for dictionaries? basically, I'd like to know how you would call every 3rd element in a list of lists... My logic says: ThirdElems=List[:][2] Which to me reads, for every item in List (which are lists), return the third item. but this doesn't work. Thanks! -- View this message in context: http://www.nabble.com/help-with-slice-tp15837808p15837808.html Sent from the Python - tutor mailing list archive at Nabble.com.

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Re: [Tutor] Problem with logic while extracting data from binary file
by bob gailer April 1, 2008

April 1, 2008

Please always reply to the list not just me. Bryan Fodness wrote: > > Thanks Bob, > > I was having trouble with that loop from the start. Could you tell me > what a=3 is doing, I cannot seem to figure it out. I accidentally left that in. It was a place for me to set a breakpoint in the debugger. I also failed to point out that I made the creation of the dictionary "search" straightforward rather than collecting all the keys and values. However neither your code or mine handles the multi-value cases (e.g. \n0\x82). To solve that I changed search to be of type defaultdict so each new element is a list and we can use append() to add values to the lists. The printed output now looks like lists but that is easy to alter. In this version I also "import time", and changed the names start and time so as not to conflict (even in appearance) with other names. Also in this version I modified parseDataElement to be a generator (the quickest way I could think of to solve the while loop problem) and added a for loop in parseDICOM to access the generator. This also required adding "start = pos" at the end of the while loop. BUT ... on further inspection of your program and data I note that there is NOTHING that looks for \n0\x82. It sits in the middle of a block of data of length 544. There needs to be some code to examine the contents of that block and look for \n0\x82. Also discovered and fixed "name 'LeafJawPostions' is not defined". Code follows ------------------------------------------------------------------ import struct import time import collections print "Creating Variables...\n" startTime = time.clock() rawData = open('file.dcm', 'rb').read() # Need to get Transfer Syntax UID (0002,0010) for encoding type def parseDICOM(data): search = collections.defaultdict(list) try: preamble, next = parsePreamble(data) except NotAPreambleException: preamble, next = None, 0 while next < len(data): for element, next, value, length in parseDataElement(data, next): if element.startswith('\n0') and element.endswith('\x00') and element[2] in ('\x10', '@', 'p', '\xb0'): start = 0 while start < length: element, start, svalue = parseSequence(value, start) search[element].append(svalue) else: search[element].append(value) return search def parsePreamble(data): preamble = data[:128] dicm = data[128:132] if dicm == 'DICM': return preamble, 132 else: raise NotAPreambleException def parseMetaElementGL(data): vl_field = data[138:140] length = struct.unpack('h', vl_field)[0] value = struct.unpack('hh',data[140:(140+length)])[0] return value def parseDataElement(data, start): if start < (144 + parseMetaElementGL(rawData)): group_num = data[start:start+2] element_num = data[start+2:start+4] vr_field = data[start+4:start+6] if vr_field in ('UN', 'SQ', 'OB','OW'): unused = data[start+6:start+8] vl_field = data[start+8:start+12] length = struct.unpack('hh', vl_field)[0] # 4-byte value = data[start+12:(start+12+length)] pos = start+12+length element = (group_num+element_num) yield element, pos, value, length else: vl_field = data[start+6:start+8] length = struct.unpack('h', vl_field)[0] # 2-byte value = data[start+8:(start+8+length)] pos = start+8+length element = (group_num+element_num) yield element, pos, value, length else: while start < len(data): group_num = data[start:start+2] element_num = data[start+2:start+4] vl_field = data[start+4:start+8] length = struct.unpack('hh', vl_field)[0] value = data[start+8:(start+8+length)] pos = start+8+length element = (group_num+element_num) yield element, pos, value, length start = pos else: print "End of File" def parseSequence(data, start): group_num = data[start:start+2] element_num = data[start+2:start+4] vl_field = data[start+4:start+8] length = struct.unpack('hh', vl_field)[0] value = data[start+8:(start+8+length)] pos = start+8+length element = (group_num+element_num) if element == '\xfe\xff\x00\xe0': start = start+8 group_num = data[start:start+2] element_num = data[start+2:start+4] vl_field = data[start+4:start+8] length = struct.unpack('hh', vl_field)[0] value = data[start+8:(start+8+length)] pos = start+8+length element = (group_num+element_num) if element == '\xfe\xff\x00\xe0': start = start+8 group_num = data[start:start+2] element_num = data[start+2:start+4] vl_field = data[start+4:start+8] length = struct.unpack('hh', vl_field)[0] value = data[start+8:(start+8+length)] pos = start+8+length element = (group_num+element_num) return element, pos, value else: return element, pos, value else: return element, pos, value # Access variables for use in calculation parsedData = parseDICOM(rawData) InstanceCreationDate = parsedData['\x08\x00\x12\x00'] InstanceCreationTime = parsedData['\x08\x00\x13\x00'] PatientsName = parsedData['\x10\x00\x10\x00'] RTPlanLabel = parsedData['\n0\x02\x00'] DoseReferenceDescription = parsedData['\n0\x16\x00'] ToleranceTableLabel = parsedData['\n0C\x00'] NumberOfBeams = int(parsedData['\n0\x80\x00'][0]) BeamDoseSpecificationPoint = parsedData['\n0\x82'] print "Instance Creation Date\t\t\t=\t%s" %InstanceCreationDate print "Instance Creation Time\t\t\t=\t%s" %InstanceCreationTime print "Patients Name\t\t\t\t=\t%s" %PatientsName print "RT Plan Label\t\t\t\t=\t%s" %RTPlanLabel print "DoseReference Description\t\t=\t%s" %DoseReferenceDescription print "Tolerance Table Label\t\t\t=\t%s" %ToleranceTableLabel print "Number Of Beams\t\t\t\t=\t%i" %NumberOfBeams print "Beam Dose Specification Point\t\t=\t%s" % BeamDoseSpecificationPoint end = time.clock() runTime = end - startTime print "\nVariables created in %.3f seconds\n" % runTime -- Bob Gailer 919-636-4239 Chapel Hill, NC

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Interactive plots...
by David Perlman April 1, 2008

April 1, 2008

I am thinking about writing a program which will involve, among other things, displaying a plot of a series of numbers. The idea is that you could click on the points and move them to change the numbers. Reverse-plotting, I suppose. It need not be complex; the numbers will all be zero or one, and it's only necessary to flip the bits, so click-and-drag is seriously overkill. Really it would be better to just double-click on a point to switch it from one value to the other. Can anyone point me in the right direction? I have written some programs in python before, including TKinter, but this new project is beyond the point that I know where to even start looking. :) In case you care, the application is in functional brain imaging; the brain scans generate a certain number of time points (say 500) and then the motion of the subject is also calculated. Standard practice is to generate a "censor" file composed of zeros and ones, where zero indicates that that time point had excessive motion and must be disregarded. I want to display a graph of the motion over time, and allow quick and easy interactive editing of the censor time series in visual parallel to the motion graph. This would save a lot of time; at present everyone does this in Excel, which being a horrible Windows program can't be integrated into the predominantly UNIX-based processing pipeline. And in any case, it requires manually typing all the zeros, looking back and forth between the graph of motion and the list of numbers. I have already written a program to algorithmically generate the censor time series from the motion data, but it is absolutely essential to be able to manually double-check and if necessary make minor edits. I'd like to be able to keep that functionality in Python rather than sending everyone back to Excel... if possible! Thanks very much for any help. -- -dave---------------------------------------------------------------- "Pseudo-colored pictures of a person's brain lighting up are undoubtedly more persuasive than a pattern of squiggles produced by a polygraph. That could be a big problem if the goal is to get to the truth." -Dr. Steven Hyman, Harvard

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Saving an Image in a Given Format
by Wayne Watson March 31, 2008

March 31, 2008

I'm pretty new to Python and libraries. I'm actually trying to modify some code someone else wrote. There are two ways images are saved. One is for the user to select a "Save as GIF" menu item, or save as tiff, or others. The other way is that the user wants a collected image from a camera saved every, say, 10 minutes. The "save" process is different for some reason. Here are the two code segments involved (NOTE my comments and questions below B.): A. Save every 10 minutes t = time.localtime(now_time) s = "a%4d%02d%02d_%02d%02d%02d.tif" % ( t.tm_year, t.tm_mon, t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec ) s = os.path.join("Exposures",s) <========== auto-exposures if not os.path.exists("Exposures"): os.mkdir("Exposures") self.current_image.save(s) <============ save image if self.trigger_mode: self.Trigger() self.CheckEvent() contrast this with where the user specifically wants the image he sees saved as a gif: B. From menu option def SaveGIF(self): if self.current_path: default_path = splitext(basename(self.current_path))[0] + ".gif" path = asksaveasfilename(defaultextension=".gif", title="Save as GIF", initialfile=default_path, filetypes=GIF_FILE_TYPES) else: path = asksaveasfilename(defaultextension=".gif", title="Save as GIF", filetypes=GIF_FILE_TYPES) if not path: return gif = self.current_image.convert("RGB") gif.save(path) <===========Save as gif. The programmer told me if I change the tif in A. to gif, jpg or whatever, it would work. Instead I get a file the of zero length when I use jpg. Can anyone explain why this wouldn't work? I see that current_image.convert is involved in one place and current_image.save in the first. What module owns these "current" methods? Hmmm, maybe I needed to use jpeg? -- Wayne Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet "The only laws of matter are those which our minds must fabricate, and the only laws of mind are fabricated for it by matter." -- James Clerk Maxwell Web Page: <www.speckledwithstars.net/>

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Re: [Tutor] Python and xml
by Konstantin Veretennicov March 29, 2008

March 29, 2008

On Sat, Mar 29, 2008 at 3:57 PM, Doran, Harold <HDoran(a)air.org> wrote: > I am a python neophyte who has used python to parse through text files > using basic functions and no OOP experience. I have a need to process some > xml files and from what I am now reading python is the exact tool I need to > work through this issue. > > However, as I read online docs and peruse which books to buy, I am quickly > becoming overwhelmed with the topic and could use some guidance on how to > best tackle my task. > > You can start with this basic example (requires Python 2.5): spam.xml: <monty> <episode number="14">Dinsdale (Face the Press)</episode> <episode number="15">The Spanish Inquisition</episode> <episode number="16">Deja vu</episode> <episode number="17">The Buzz Aldrin Show</episode> <episode number="18">Live From the Grill-O-Mat Snack Bar</episode> <episode number="19">It's a Living</episode> <episode number="20">The Attila the Hun Show</episode> <episode number="21">Archaeology Today</episode> <episode number="22">How to Recognize Different Parts of the Body</episode> <episode number="23">Scott of the Antarctic</episode> <episode number="24">How Not to Be Seen</episode> <episode number="25">Spam</episode> <episode number="26">Royal Episode 13</episode> </monty> spam.py: from xml.etree.ElementTree import ElementTree as ET et = ET(file='spam.xml') for episode in et.findall('episode'): print episode.attrib['number'] + ':', '"' + episode.text + '"' Use standard csv module if you want to produce csv ouput ( http://docs.python.org/lib/module-csv.html). -- kv

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