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  • Multithreading or task parallel library

    - by Bruce Adams
    I have an application which performs 30 independent tasks simultaneously using multithreading, each task retrieves data over http, performs a calculation and returns a result to the ui thread. Can I use tpl to perform the same tasks? Does tpl create 30 new threads and spread them over all the available cores, or does it just split the tasks over the available cores and use one thread per core? Will there be a performance boost using tpl over multithreading in this case?

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  • Python: two loops at once

    - by Stephan Meijer
    I've got a problem: I am new to Python and I want to do multiple loops. I want to run a WebSocket client (Autobahn) and I want to run a loop which shows the filed which are edited in a specific folder (pyinotify or else Watchdog). Both are running forever, Great. Is there a way to run them at once and send a message via the WebSocket connection while I'm running the FileSystemWatcher, like with callbacks, multithreading, multiprocessing or just separate files? factory = WebSocketClientFactory("ws://localhost:8888/ws", debug=False) factory.protocol = self.webSocket connectWS(factory) reactor.run() If we run this, it will have success. But if we run this: factory = WebSocketClientFactory("ws://localhost:8888/ws", debug=False) factory.protocol = self.webSocket connectWS(factory) reactor.run() # Websocket client running now,running the filewatcher wm = pyinotify.WatchManager() mask = pyinotify.IN_DELETE | pyinotify.IN_CREATE # watched events class EventHandler(pyinotify.ProcessEvent): def process_IN_CREATE(self, event): print "Creating:", event.pathname def process_IN_DELETE(self, event): print "Removing:", event.pathname handler = EventHandler() notifier = pyinotify.Notifier(wm, handler) wdd = wm.add_watch('/tmp', mask, rec=True) notifier.loop() This will create 2 loops, but since we already have a loop, the code after 'reactor.run()' will not run at all.. For your information: this project is going to be a sync client. Thanks a lot!

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  • Java PlayFramework & Python Django GAE

    - by Maik Klein
    I already know Java, C# and C++. Now I want to start with web development and I saw that some really big sites are built with Python/C++. I like the coding style of Python, it looks really clean, but some other things like no errors before runtime is really strange. However, I don't know what I should learn now. I started with Python but then I saw that Google App Engine also supports Java and the PlayFramework looks amazing too. Now I am really confused. Should I go with Python or Java? I found the IDE for Python "PyCharm" really amazing for web development. Does Java have something similar, eclipse maybe? I know that this question isn't constructive, but it will help me with my decision. What are pro and cons of both languages?

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  • How to familiarize myself with Python

    - by Zel
    I am Python beginner. Started Python 1.5 months back. I downloaded the Python docs and read some part of the tutorial. I have been programming on codechef.com and solving problems of projecteuler. I am thinking of reading Introduction to algorithms and following this course on MIT opencourse ware as I haven't been getting much improvement in programming and I am wasting much time thinking just what should I do when faced with any programming problem. But I think that I still don't know the correct way to learn the language itself. Should I start the library reference or continue with Python tutorial? Is learning algorithms useful for language such as C and not so much for Python as it has "batteries included"? Are there some other resources for familiarization with the language and in general for learning to solve programming problems? Or do I need to just devote some more time?

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  • Convertion of tiff image in Python script - OCR using tesseract

    - by PYTHON TEAM
    I want to convert a tiff image file to text document. My code perfectly as I expected to convert tiff images with usual font but its not working for french script font . My tiff image file contains text. The font of text is in french script format.I here is my code import Image import subprocess import util import errors tesseract_exe_name = 'tesseract' # Name of executable to be called at command line scratch_image_name = "temp.bmp" # This file must be .bmp or other Tesseract-compatible format scratch_text_name_root = "temp" # Leave out the .txt extension cleanup_scratch_flag = True # Temporary files cleaned up after OCR operation def call_tesseract(input_filename, output_filename): """Calls external tesseract.exe on input file (restrictions on types), outputting output_filename+'txt'""" args = [tesseract_exe_name, input_filename, output_filename] proc = subprocess.Popen(args) retcode = proc.wait() if retcode!=0: errors.check_for_errors() def image_to_string(im, cleanup = cleanup_scratch_flag): """Converts im to file, applies tesseract, and fetches resulting text. If cleanup=True, delete scratch files after operation.""" try: util.image_to_scratch(im, scratch_image_name) call_tesseract(scratch_image_name, scratch_text_name_root) text = util.retrieve_text(scratch_text_name_root) finally: if cleanup: util.perform_cleanup(scratch_image_name, scratch_text_name_root) return text def image_file_to_string(filename, cleanup = cleanup_scratch_flag, graceful_errors=True): If cleanup=True, delete scratch files after operation.""" try: try: call_tesseract(filename, scratch_text_name_root) text = util.retrieve_text(scratch_text_name_root) except errors.Tesser_General_Exception: if graceful_errors: im = Image.open(filename) text = image_to_string(im, cleanup) else: raise finally: if cleanup: util.perform_cleanup(scratch_image_name, scratch_text_name_root) return text if __name__=='__main__': im = Image.open("/home/oomsys/phototest.tif") text = image_to_string(im) print text try: text = image_file_to_string('fnord.tif', graceful_errors=False) except errors.Tesser_General_Exception, value: print "fnord.tif is incompatible filetype. Try graceful_errors=True" print value text = image_file_to_string('fnord.tif', graceful_errors=True) print "fnord.tif contents:", text text = image_file_to_string('fonts_test.png', graceful_errors=True) print text

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  • Typing commands into a terminal always returns "-bash: /usr/bin/python: is a directory"

    - by Artur Sapek
    I think I messed something up on my Ubuntu server while trying to upgrade to Python 2.7.2. Every time I type in a command that doesn't have a response, the default from bash is this: -bash: /usr/bin/python: is a directory Just like it would say if I typed the name of a directory. But this happens every time I enter a command that doesn't do anything. artur@SERVER:~$ dslkfjdsklfdshjk -bash: /usr/bin/python: is a directory I remember messing with the update-alternatives to point at python at some point, perhaps that could be it? Any inklings as to why this is happening? Related to this problem is also the fact that when I try using easy_install it tells me -bash: /usr/bin/easy_install: /usr/bin/python: bad interpeter: Permission denied /etc/fstab/ is set to exec. I've read that could fix the second problem but it hasn't.

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  • How to make a python script run in Anacron

    - by Jeremy
    I have a python script that I would like to run daily using anacron, but I haven't been able to get it to work. The script is in my home directory, and I have put a symlink to it in /etc/cron.daily/. I saw somewhere that things here can't have dots in the filename, so the symlink has the .py extension removed (the original file still has it). The python file does have #!/usr/bin/python on the first line. This is my first experience with cron / anacron, and so I'm sure I'm making a dumb mistake - I just don't know what it is. Is a symlink a problem? Do I need the actual file there? Is the python script the problem? Do I need to run a bash script that will open the python script? Is there something else I'm not thinking of?

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  • Python script as a service on Ubuntu 11.10

    - by bugs99
    I am facing the following problem. I want to run a python script as a service on Ubuntu 11.10 system (already mentioned in the following link: Python service using Upstart on Ubuntu) I followed the steps mentioned in the above mentioned link, but i got the following error message in syslog: init: script main process (21826) terminated with status 1 Jun 8 16:59:55 bilbo kernel: [263012.984531] init: script main process ended, respawning Jun 8 16:59:55 bilbo kernel: [263013.044099] init: script main process (21827) terminated with status 1 The above two lines are getting repeated all the time. On saying sudo start script, I get the following: $ sudo start script script start/running, process 21826 Following is the content of my script.conf placed in /etc/init: description "Used to start python script as a service" author "bilbo" start on runlevel [2] stop on runlevel [06] exec python /home/bilbo/scripts/webserver.py respawn Please tell me what I am doing wrong? Do I have to change my python code as well?

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  • How to install Visual Python?

    - by user214152
    I'm a Linux newbie but I'm determined to get my favorite applications on my laptop running Ubuntu 12.04. I just installed Cinnamon. I'm trying to install Visual Python and it requires Python 2.7. I followed the instructions on the VPython site but the Wine application isn't extracting anything from the Python .msi file. From the first line wine start /i python-2.7.5.amd64.msi /qn TARGETDIR=~/Python27 ALLUSERS=1 it says fixme:storage:create_storagefile Storage share mode not implemented. I created that Python27 directory so I know it exists and it's empty. I know Ubuntu already has Python 2.7 so I just tried running the VPython.exe file but it says "This program can only be installed on versions of Windows designed for the following processor architectures: x64." My Toshiba satellite has a 64-bit processor. Could anybody help?

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  • Python repl in python application

    - by Olorin
    Hello i am learning python(so i can use qt with python not only c++) and i'm curios if it would be possible to embed a python interpreter in my application as a repl. I would like to give users to possibility to script the app using python either loading a file (and that file to act as a plugin for the app) or by evaluating code entered in a text box or something like that. Just like you can embed the interpreter in C or C++ and script the app using python can this be done if the application is itself written in python(and made a stand-alone binary using py2exe or something similar)? something like Anders did with the C# repl or Miguel with mono. Thanks.

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  • Using Python on Mac

    - by choise
    hi, i want to learn python using my mac. now i want to setup a python version = 3.1.3, because my materials for learning are using this version. typing python into terminal results version 2.6.1, using the dmg installer on python.org (http://docs.python.org/ftp/python/3.1.3/) doesn't have an effect on the python version in terminal, but it's bundled with an own shell under Applications/Python 3.1/Idle.app my question now is, should i use this shell for learing or is there a better way, updating the python version bundled with snow leopard? i already tried defaults write com.apple.versioner.python Version 3.1.3 or defaults write com.apple.versioner.python Version 3.0 without any result. thanks!

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  • Until when will Python 2.5 be supported?

    - by Emilien
    Apparently Python only supports 2 minor versions (like 2.X), so that would mean Python 2.5 would get phased out when Python 2.7 comes out (in June 2010?) Is this correct? PEP 356 -- Python 2.5 Release Schedule doesn't give much answers to this question.

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  • No IDLE for Python 3?

    - by NotSuper
    I installed Python 3.1 yesterday on my Windows Vista PC, and was surprised to find that the version of IDLE is 2.6.4, for "Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)] on win32" I was hoping to use IDLE to investigate some of the new features of Python 3... I guess I'm stuck with the command line... Anyone know what's up with Python 3's IDLE? Thanks

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  • How to implement a Mutex in Python when using Gtk with PyGTK

    - by Julian
    Hi, I have an application that starts several threads using gobject.timeout_add(delay, function) Now in my function I want to test and set on some variable, e.g. def function(self): if flag == True: flag = False doSomething() Now to make this threadsafe, I would have to lock the function using some mutex lock. Is this possible with Gtk? Or can I use the Python Lock objects from threading?

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  • How to share a dictionary between multiple processes in python without locking

    - by RandomVector
    I need to share a huge dictionary (around 1 gb in size) between multiple processs, however since all processes will always read from it. I dont need locking. Is there any way to share a dictionary without locking? The multiprocessing module in python provides an Array class which allows sharing without locking by setting lock=false however There is no such option for Dictionary provided by manager in multiprocessing module.

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  • Why use Python interactive mode?

    - by mvid
    When I first started reading about Python, all of the tutorials have you use Python's Interactive Mode. It is difficult to save, write long programs, or edit your existing lines (for me at least). It seems like a far more difficult way of writing Python code than opening up a code.py file and running the interpreter on that file. python code.py I am coming from a Java background, so I have ingrained expectations of writing and compiling files for programs. I also know that a feature would not be so prominent in Python documentation if it were not somehow useful. So what am I missing?

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  • Boost.Python tutorial in Ubuntu 10.04

    - by Doughy
    I downloaded the latest version of Boost and I'm trying to get the Boost.python tutorial up and running on Ubuntu 10.04: http://www.boost.org/doc/libs/1_43_0/libs/python/doc/tutorial/doc/html/python/hello.html I navigated to the correct directory, ran "bjam" and it compiled using default settings. I did not yet create a bjam config file. The compilation appears to have worked, but now I have no idea how to include the files in my python script. When I try to run the python hello world script, it gives me this error: Traceback (most recent call last): File "./hello.py", line 6, in <module> import hello_ext ImportError: libboost_python.so.1.43.0: cannot open shared object file: No such file or directory Anyone know what is going on?

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  • Avoiding accidentally catching KeyboardInterrupt and SystemExit in Python 2.4

    - by jrdioko
    In Python scripts, there are many cases where a keyboard interrupt (Ctrl-C) fails to kill the process because of a bare except clause somewhere in the code: try: foo() except: bar() The standard solution in Python 2.5 or higher is to catch Exception rather than using bare except clauses: try: foo() except Exception: bar() This works because, as of Python 2.5, KeyboardInterrupt and SystemExit inherit from BaseException, not Exception. However, some installations are still running Python 2.4. How can this problem be handled in versions prior to Python 2.5? (I'm going to answer this question myself, but putting it here so people searching for it can find a solution.)

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  • Python thread pool similar to the multiprocessing Pool?

    - by Martin
    Is there a Pool class for worker threads, similar to the multiprocessing module's Pool class? I like for example the easy way to parallelize a map function def long_running_func(p): c_func_no_gil(p) p = multiprocessing.Pool(4) xs = p.map(long_running_func, range(100)) however I would like to do it without the overhead of creating new processes. I know about the GIL. However, in my usecase, the function will be an IO-bound C function for which the python wrapper will release the GIL before the actual function call. Do I have to write my own threading pool?

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  • Python threads all executing on a single core

    - by Rob Lourens
    I have a Python program that spawns many threads, runs 4 at a time, and each performs an expensive operation. Pseudocode: for object in list: t = Thread(target=process, args=(object)) # if fewer than 4 threads are currently running, t.start(). Otherwise, add t to queue But when the program is run, Activity Monitor in OS X shows that 1 of the 4 logical cores is at 100% and the others are at nearly 0. Obviously I can't force the OS to do anything but I've never had to pay attention to performance in multi-threaded code like this before so I was wondering if I'm just missing or misunderstanding something. Thanks.

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  • Python - question regarding the concurrent use of `multiprocess`.

    - by orokusaki
    I want to use Python's multiprocessing to do concurrent processing without using locks (locks to me are the opposite of multiprocessing) because I want to build up multiple reports from different resources at the exact same time during a web request (normally takes about 3 seconds but with multiprocessing I can do it in .5 seconds). My problem is that, if I expose such a feature to the web and get 10 users pulling the same report at the same time, I suddenly have 60 interpreters open at the same time (which would crash the system). Is this just the common sense result of using multiprocessing, or is there a trick to get around this potential nightmare? Thanks

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  • Parent Thread exiting before Child Threads [python]

    - by crgwbr
    I'm using Python in a webapp (CGI for testing, FastCGI for production) that needs to send an occasional email (when a user registers or something else important happens). Since communicating with an SMTP server takes a long time, I'd like to spawn a thread for the mail function so that the rest of the app can finish up the request without waiting for the email to finish sending. I tried using thread.start_new(func, (args)), but the Parent return's and exits before the sending is complete, thereby killing the sending process before it does anything useful. Is there anyway to keep the process alive long enough for the child process to finish?

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  • Way to kill python thread from inside thread?

    - by user859434
    I have some python code that currently performs expensive computation by performing the computation in parallel through many threads. For a given time period, many threads are created and started on the fly that share the same code which is explicitly stated within the run method of the thread. My question is how do I stop/kill a thread at the end of its run method? (the run is only called once) I need to do this in order to create more threads for the next batch of computation. #Example class someThread(threading.Thread): def __init__(self): #some init code def run(self): #Explicitly Stated Code without constant loops #Something performed to stop/kill this thread

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  • How can I tell if I am overusing multi-threading?

    - by exhuma
    NOTE: This is a complete re-write of the question. The text before was way too lengthy and did not get to the point! If you're interested in the original question, you can look it up in the edit history. I currently feel like I am over-using multi-threading. I have 3 types of data, A, B and C. Each A can be converted to multiple Bs and each B can be converted to multiple Cs. I am only interested in treating Cs. I could write this fairly easily with a couple of conversion functions. But I caught myself implementing it with threads, three queues (queue_a, queue_b and queue_c). There are two threads doing the different conversions, and one worker: ConverterA reads from queue_a and writes to queue_b ConverterB reads from queue_b and writes to queue_c Worker handles each element from queue_c The conversions are fairly mundane, and I don't know if this model is too convoluted. But it seems extremely robust to me. Each "converter" can start working even before data has arrived on the queues, and at any time in the code I can just "submit" new As or Bs and it will trigger the conversion pipeline which in turn will trigger a job by the worker thread. Even the resulting code looks simpler. But I still am unsure if I am abusing threads for something simple.

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  • Make Python Socket Server More Efficient

    - by BenMills
    I have very little experience working with sockets and multithreaded programming so to learn more I decided to see if I could hack together a little python socket server to power a chat room. I ended up getting it working pretty well but then I noticed my server's CPU usage spiked up over 100% when I had it running in the background. Here is my code in full: http://gist.github.com/332132 I know this is a pretty open ended question so besides just helping with my code are there any good articles I could read that could help me learn more about this? My full code: import select import socket import sys import threading from daemon import Daemon class Server: def __init__(self): self.host = '' self.port = 9998 self.backlog = 5 self.size = 1024 self.server = None self.threads = [] self.send_count = 0 def open_socket(self): try: self.server = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.server.bind((self.host,self.port)) self.server.listen(5) print "Server Started..." except socket.error, (value,message): if self.server: self.server.close() print "Could not open socket: " + message sys.exit(1) def remove_thread(self, t): t.join() def send_to_children(self, msg): self.send_count = 0 for t in self.threads: t.send_msg(msg) print 'Sent to '+str(self.send_count)+" of "+str(len(self.threads)) def run(self): self.open_socket() input = [self.server,sys.stdin] running = 1 while running: inputready,outputready,exceptready = select.select(input,[],[]) for s in inputready: if s == self.server: # handle the server socket c = Client(self.server.accept(), self) c.start() self.threads.append(c) print "Num of clients: "+str(len(self.threads)) self.server.close() for c in self.threads: c.join() class Client(threading.Thread): def __init__(self,(client,address), server): threading.Thread.__init__(self) self.client = client self.address = address self.size = 1024 self.server = server self.running = True def send_msg(self, msg): if self.running: self.client.send(msg) self.server.send_count += 1 def run(self): while self.running: data = self.client.recv(self.size) if data: print data self.server.send_to_children(data) else: self.running = False self.server.threads.remove(self) self.client.close() """ Run Server """ class DaemonServer(Daemon): def run(self): s = Server() s.run() if __name__ == "__main__": d = DaemonServer('/var/servers/fserver.pid') if len(sys.argv) == 2: if 'start' == sys.argv[1]: d.start() elif 'stop' == sys.argv[1]: d.stop() elif 'restart' == sys.argv[1]: d.restart() else: print "Unknown command" sys.exit(2) sys.exit(0) else: print "usage: %s start|stop|restart" % sys.argv[0] sys.exit(2)

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