🌐 Mailman 3 November 2004 - Tutor - python.org

How to calculate pi with this formula?
by Dick Moores April 14, 2005

April 14, 2005

Is it possible to calculate almost-pi/2 using the (24) formula on <http://mathworld.wolfram.com/PiFormulas.html> without using (23)? If it's possible, how about a hint? Recursion? Thanks, tutors. Dick Moores rdm(a)rcblue.com

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Output to a printer
by Bob Fleming Dec. 29, 2004

Dec. 29, 2004

I am learning Python on a Windows system (Win95). All of the tutorials, documentation, and a book that I am studying all assume printing to the console (stdout). I live in the real world and will need to print out to my laser printer or other device. How do I modify the print or write statements, or redirect stdout, to print to a printer? Thank you, Bob Fleming robertf(a)eskimo.com

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RE: [Tutor] Debugging in emacs
by McLaughlin, Toby Dec. 27, 2004

Dec. 27, 2004

Thanks Marilyn, Debugging in emacs is obviously not the hottest topic around here. Luckily, I have something working now. For anyone who is interested, here is the trick: 1. Add the following to your program: import pdb pdb.set_trace() 2. Start an interactive Python buffer (C-c !) 3. Run your program (I use C-c C-c) Emacs picks up the line numbers from set_trace() and marks the appropriate line in the source buffer. You can now type 'n' to single step, as well as issue any of the pdb commands mentioned here: http://tinyurl.com/3na4u . The only trouble I have now is that the Python buffer and my source code keep switching places from top to bottom. A minor annoyance that hopefully I will rectify soon. Toby McLaughlin. > -----Original Message----- > From: Marilyn Davis [mailto:marilyn@deliberate.com] > Sent: Saturday, 20 November 2004 9:28 AM > To: McLaughlin, Toby > Cc: tutor(a)python.org > Subject: Re: [Tutor] Debugging in emacs > > > On Fri, 19 Nov 2004, McLaughlin, Toby wrote: > > > Hi All, > > > > Could somebody suggest a way to debug python in emacs? I'd > like to be > > able to single-step while seeing the code marked in some way and > > possiblly set breakpoints. I read about using pdb from the > command line > > but would love to have debugging integrated in emacs. > Perhaps I should > > make life easy for myself and use one of the fancy GUI > editors, but I > > think it's character building for me to learn emacs. > > Boy, you could hear a pin drop on this topic. > > I use emacs, even though I have spent some time with idle, because I > like it much better. I'm real handy in emacs though, and I don't like > mousing. Mice cause lots of repetitive stress injury. > > I spent some time and some email conversations trying to make use of > the debugger in any environment. I don't remember what happened > exactly but I gave up. > > The thing about an interpreted language is that you can say "print > my_var" in the code instead of in the debugger. And with emacs, I go > back and forth between my code and the emacs shell to run it. I'm > pretty efficient that way. > > If anyone has any suggestions about debugging, in idle or anywhere, I > too would love to hear them. > > Thank you. > > Marilyn Davis > > > > > > Thanks, > > Toby McLaughlin. > > _______________________________________________ > > Tutor maillist - Tutor(a)python.org > > http://mail.python.org/mailman/listinfo/tutor > > > > -- > >

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comapring lists
by Jim De Caro Dec. 5, 2004

Dec. 5, 2004

I am getting user input and comparing it to an iterated list. I can get the input to print out verbatim. I want to then "swap" individual letters in the input with letters from a second list so it is like a simple encryption. I can't figure out the correct logic or syntax. Here is what I have so far: user = raw_input("Enter your selection: ") encrypt = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','0','1','2','3','4','5','6','7','8','9','0'] decrypt =['b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','a','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','A','0','1','2','3','4','5','6','7','8','9','0'] for i in range(len(encrypt)): print user[0:62] break for j in range(len(decrypt)): for j in zip(decrypt): print 'Encrypted-> %s' % (j,user) break This does not work. Any suggestions? Thanks Jim DeCaro Microsoft Certified Systems Engineer Windows 2000 - Windows NT 4.0 + Internet

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new function and a 3 line program not working
by Tim Moffatt Dec. 3, 2004

Dec. 3, 2004

This is my first post, so HI all! and thank you for you help! Below is a tutorial that I am trying to complete, but I can not duplicate this exercise in either the IDLE gui or command line. (ver 2.3.4) Tutorial says do this go to IDLE gui and define the new function def newLine(): print then i open another IDLE window and write the 3 line program like in the tutorial print "First Line." newLine() print "Second Line." save it as line.py Now I am to see this output result upon running it First line. Second line. But I dont get this, I get a First line." printed and a syntax error >>> First Line. Traceback (most recent call last): File "C:/Python23/newLine.py", line 2, in -toplevel- newLine() NameError: name 'newLine' is not defined >>> complete lesson below 3.6 Adding new functions So far, we have only been using the functions that come with Python, but it is also possible to add new functions. Creating new functions to solve your particular problems is one of the most useful things about a general-purpose programming language. In the context of programming, a function is a named sequence of statements that performs a desired operation. This operation is specified in a function definition. The functions we have been using so far have been defined for us, and these definitions have been hidden. This is a good thing, because it allows us to use the functions without worrying about the details of their definitions. The syntax for a function definition is: def NAME( LIST OF PARAMETERS ): STATEMENTS You can make up any names you want for the functions you create, except that you can't use a name that is a Python keyword. The list of parameters specifies what information, if any, you have to provide in order to use the new function. There can be any number of statements inside the function, but they have to be indented from the left margin. In the examples in this book, we will use an indentation of two spaces. The first couple of functions we are going to write have no parameters, so the syntax looks like this: def newLine(): print This function is named newLine. The empty parentheses indicate that it has no parameters. It contains only a single statement, which outputs a newline character. (That's what happens when you use a printcommand without any arguments.) The syntax for calling the new function is the same as the syntax for built-in functions: print "First Line." newLine() print "Second Line." The output of this program is: First line. Second line. Notice the extra space between the two lines. What if we wanted more space between the lines? We could call the same function repeatedly: print "First Line." newLine() newLine() newLine() print "Second Line." Or we could write a new function named threeLines that prints three new lines: def threeLines(): newLine() newLine() newLine() print "First Line." threeLines() print "Second Line." This function contains three statements, all of which are indented by two spaces. Since the next statement is not indented, Python knows that it is not part of the function. You should notice a few things about this program: 1. You can call the same procedure repeatedly. In fact, it is quite common and useful to do so. 2. You can have one function call another function; in this case threeLines calls newLine. So far, it may not be clear why it is worth the trouble to create all of these new functions. Actually, there are a lot of reasons, but this example demonstrates two: * Creating a new function gives you an opportunity to name a group of statements. Functions can simplify a program by hiding a complex computation behind a single command and by using English words in place of arcane code. * Creating a new function can make a program smaller by eliminating repetitive code. For example, a short way to print nine consecutive new lines is to call threeLines three times. As an exercise, write a function called nineLines that uses threeLines to print nine blank lines. How would you print twenty-seven new lines?

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programming newbie question
by dustinp＠pointclark.net Dec. 3, 2004

Dec. 3, 2004

I am fairly new to programming and I have started to learn programming then stopped out of frustration several times in the past. I guess my frustration stems from not being able to understand when to use certain aspects of programming such as functions or classes. I have read enough books and tutorials to know the syntax of python and I understand most everything related to the concepts of programming, but I have never been able to put it all together and learn how and when to use specific features. Can anyone suggest a method or some reading to help out with this? I also struggle with finding projects to work on does anyone know of projects that a novice could contribute to?

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Pythonw.exe doesn't work in the python2.4 distribution?
by Jacob S. Dec. 3, 2004

Dec. 3, 2004

Hi everybody. I just installed Python2.4 by my Python2.3 folder in the C directory. I'm running WindowsXP. I tried to run any scripts of mine afterwards, but they didn't work. After messing with file associations, I finally can execute the scripts using python24. However, the "Edit with IDLE" command in the shorcut menu (right-click pull down menu) no longer worked. So I went to the registry (I know the risks involved) and checked out the commands and the like. I found a key named Python.File which had subsequent keys Shell,Edit with IDLE, and command. In the command key, there was a string value that told the shortcut menu to run the command "C:\python24\pythonw.exe" "C:\python24\lib\idlelib\idle.pyw -n -e %1" when Edit with IDLE was selected from the shortcut menu. I played with the above string doing things like "C:\python24\pythonw.exe" "C:\python24\lib\idlelib\idle.py -n-e %1", and I even tried using the idle.bat file in the directory. The only time it worked was when I change pythonw.exe to python.exe. Now this is fine and dandy, but I want IDLE to run without a console. So currently, the above string reads, "C:\python23\pythonw.exe" "C:\python24\lib\idlelib\idle.pyw -n -e %1" A few things... 1) Can anyone explain why pythonw.exe doesn't do what it is supposed to do in python24? 2) Can anyone directo me to a new pythonw.exe that works? Is all of the python included in the pythonXX.dll? IOW, could I copy the pythonw.exe file from the python23 distribution and still have all the functionality of python24? 3) Can anyone off-hand tell me what the arguments -n and -e mean in the above string? Does anybody know of a list of these? (Not urgent, if no one knows, I won't bother extensively searching for one.) Thanks in advance for anyone who can help with the above three things. Jacob Schmidt

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RE: how to zip data? (Branimir Petrovic)
by Eri Mendz Dec. 2, 2004

Dec. 2, 2004

Hello list, I'm trying to understanding this zip code. Can you kindly explain what's happening step by step? The try: finally clause is something new. And also what does the below code do? I see this always in the codes in this group. I seem not to encounter this (yet) in my tutorial reference. TIA > if __name__=="__main__": -- Regards, erimendz Gmail Google Mail >> -----Original Message----- >> From: Ramkumar Parimal Alagan [mailto:ramster6@gmail.com] [snip] >> zip_command = "zip -qr '%s' %s" % (target, ' '.join(source)) >> >> if os.system(zip_command) == 0: >> print 'Successful backup to', target >> else: >> print 'Backup FAILED' >> > """No such a thing as "zip" command/utility on Windows, but using > Python's standard library you could build your own.... > > Example below shows how to gz-ip a file (if you wonder why .gz and > not .zip: gzip library compresses as good and has no upper limit > on how large file it can process). > > If below example looks too involving, you could purchase WinZip > and get command line utility that will zip files for you via > os.system call (but beware - WinZip can not zip/unzip files larger > than 4 GB) > > Branimir > """ > > ###################################################################### > # FileName gzDemo.py > ###################################################################### > > import exceptions, os, re, gzip > > def gzipIt(filetogzip, gzippedname=None): > """Will GZIP file whose path is described by 'filetogzip' string. > > Parameters: > filetogzip, gzippedname - STRING > > By default (if 'gzippedname' not supplied):, > - will gunzip 'filetogzip' to same folder with the source file, > - will add '.gz' suffix to file name > - will remove source file after successful gzipping. > > If 'gzippedname' is supplied, the source ('filetogzip') is not removed. > > Works like a charm although is 20% slower than GNU's gunzip utility. > """ > > chunksize=1048576 > removesource = False > > if not gzippedname: > gzippedname = filetogzip + r'.gz' > removesource = True > > inputfile = file(filetogzip, r'rb', chunksize) > try: > chunkdata = inputfile.read(chunksize) > gzoutfile = gzip.open(gzippedname, mode='wb', compresslevel=5) > try: > while chunkdata: > gzoutfile.write(chunkdata) > chunkdata = inputfile.read(chunksize) > finally: > gzoutfile.close() > finally: > inputfile.close() > > if removesource: os.remove(filetogzip) > > > def gunzipIt(filetogunzip, gunzippedname=None): > """Will GUNZIP file whose path is described by 'filetogzip' string. > > Parameters: > filetogunzip, gunzippedname - STRING > > By default (if 'gunzippedname' not supplied):, > - will gunzip 'filetogunzip' to same folder with the source file, > - will strip '.gz' from file name suffix and > - will remove source file after successful gunzipping. > > If 'gunzippedname' is supplied, the source ('filetogunzip') is not > removed. > > Works like a charm although is 30% slower than GNU's gunzip utility. > """ > > chunksize=8192 > removesource = False > > if not gunzippedname: > # strip '.gz' off the end of gzippedname > gunzippedname = re.sub('(\.(g|G)(z|Z))', '', filetogunzip) > removesource = True > > fgunzip = gzip.open(filetogunzip, mode='rb') > try: > chunkdata = fgunzip.read(chunksize) > foutput = file(gunzippedname, r'wb', chunksize) > try: > while chunkdata: > foutput.write(chunkdata) > chunkdata = fgunzip.read(chunksize) > finally: > foutput.close() > finally: > fgunzip.close() > > if removesource: os.remove(filetogunzip) > > > > > if __name__=="__main__": > > try: > # 1st run will "do-it:" > toZip = r'C:\_b\textStuff.txt' > gzipIt(toZip) > except exceptions.IOError: > # 2nd run will "un-do-it": > try: > toUnZip = r'C:\_b\textStuff.txt.gz' > gunzipIt(toUnZip) > except exceptions.IOError: > pass > >

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Cannot cPickle.load()
by Hugo González Monteverde Dec. 1, 2004

Dec. 1, 2004

Hi Tutors, I think I must be missing something here. I pickled a dictionary of lists into a file, using protocol 2, some weeks ago. Now I'm trying to load it and I can't. File is 21kB long, so I know it has data in it, and when I read it into a string (without pickling) I understand the pickle is there. Here's my log: IDLE 1.0.3 >>> import cPickle >>> import pickle >>> myfilep=open("e:\Devel\listpickled", "r") >>> myfilep <open file 'e:\Devel\listpickled', mode 'r' at 0x00AA05A0> >>> mydict = cPickle.load(myfilep) Traceback (most recent call last): File "<pyshell#4>", line 1, in -toplevel- mydict = cPickle.load(myfilep) EOFError >>> myfilep.tell() 4096L >>> myfilep.seek(0) >>> mydict= pickle.load(myfilep) Traceback (most recent call last): File "<pyshell#7>", line 1, in -toplevel- mydict= pickle.load(myfilep) File "C:\Python23\lib\pickle.py", line 1390, in load return Unpickler(file).load() File "C:\Python23\lib\pickle.py", line 872, in load dispatch[key](self) File "C:\Python23\lib\pickle.py", line 1189, in load_binput i = ord(self.read(1)) TypeError: ord() expected a character, but string of length 0 found >>> myfilep.tell() 512L >>> myfilep.seek(0) >>> mystring = myfilep.read() >>> mystring '\x80\x02]q\x01(U\x05Aaronq\x02U\x04Abelq\x03U\x08Abelardoq\x04U\x07Abelinoq\x05U\x07Abigailq\x06U\x07Abrahamq\x07U\x05Abrilq\x08U\x06Abundiq\tU\x03Adaq\nU\x05Adahiq\x0bU\x06Adalayq\x0cU\tAdalbertoq\rU\x08Adalgisaq\x0eU\x06Adalidq\x0fU\x07Adamariq\x10U\x04Adelq\x11U\x05Adelaq\x12U\x08Adelaidaq\x13U\x07Adelinaq\x14U\x06Adizonq\x15U\x06Adolfoq\x16U\x06Adonayq\x17U\x06Adrianq\x18U\x07Adrianaq\x19U\x04Ad\xe1nq' >>> #But this is not the full contents of the file! >>> myfilep.tell() 20480L >>> len(mystring) 257 >>> mystring = myfilep.read() >>> len(mystring) 157 >>> mystring = myfilep.read() >>> len(mystring) 0 >>> #ok, done with the reading >>> I cannot make any sense of it. Both implementations of load() tell me they're encountering EOF right away. If I use read, there's the pickled data, but I cannot read the entire file into the variable. Please help if possible. I don't know what elese to do... (!) Hugo

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(no subject)
by Jeff Peery Dec. 1, 2004

Dec. 1, 2004

hello again, I am thoroughly confused. I am using Timer from the threading module. I want to check a specific file every few minutes to see if it has been altered (I do this by checking the size of the file using stat) if it hasn't then I do nothing, if it has then I attempt to read the file, grab all the new numerical data and update a graph on my computer. this file I am reading holds liquid volumetric flow rate measurement data and the python code I am writing is to be used as a statistical process control. basically I watch the results from the measurements by watching a particular file for updates, when an update occurs I grab the data do some more stats, then update my graphs that show on my desktop. the timer I used is a class, so I defined a new object (I think thats the right word) as: myTimer = Timer(30.0, Update) where the timer runs every 30 seconds and Update is a function that checks if the file has been altered and if so then it updates my graphs. I then start the timer: myTimer.start() I am confused by two things: 1) I want my timer to restart every 30 seconds. as it shows above it will go just one time. If I put this in a while loop, will the while loop loop through the start command faster than 30 second intervals or will it wait for the timer to execute the Update function before calling timer.start() again? 2) I am also confused about how variables are handled when I have multiple and nested functions. for example, I would like to initiate the Update function every 30 seconds and I want the Update funtion to return any new data. how can I return something from a function when the function is called from a timer? I cannot do an assignment statement from within the definnition of myTimer? or do I even need to return the data? if I create a variable in the update function is it available in my main function? I am not sure how python handles variables that are defined in different functions. thank you very much for spending the time to help me, I appreciate it! Jeff

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