Re: How to get a raised exception from other thread
One suggestion about the above: description is actually the exception instance (the object), not just the description. Yes. In fact, it's a tuple. Maybe, I'll change it for just printing the second item of it. Thanks a lot. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
dcrespo wrote: Ok, sorry about the above question. I solved it adding this to the main thread: try: SrvrTCP = module.ThreadedTCPServer(ip,port) SrvrTCP.start() except Exception, description: MsgBox(self,TCPServer Error:\n\n+str(description),title=TCPServer,style=wx.OK | wx.ICON_ERROR) return Peter, thank you very much. You're quite welcome. It's nice to be able to provide a perfect answer, for a change. :-) One suggestion about the above: description is actually the exception instance (the object), not just the description. The except statement can take two items after: the exception type(s) to catch and, optionally, a name to bind to the exception instance. But since exception objects know how to represent themselves as strings, calling str() on it gives you the description you wanted. Therefore it would be more readable/correct to say this: except Exception, ex: MsgBox(. str(ex) ... ) But I'm happy it works either way! -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Peter Hansen wrote: [EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. As Dennis points out, your original attempt was destined to fail because you were calling the method from the main thread, not the one you wanted to kill. Threads don't magically execute any methods that are attached to the Thread instance just because they're attached. You have to actually call those methods *from* the thread, which means from the run() method or from any of the routines it calls (whether they are methods on that Thread or not), but it must be done in the context of the thread you want to raise exceptions in or it won't work. More importantly, you've now described your use case (and I hope that of the OP as well, since he hasn't replied yet): killing threads. This is an oft-discussed topic here, and searching the archives will probably give you lots more answers, but the short answer is you cannot kill a thread in Python (except by exiting the entire process). Instead, as you've discovered, you must ask it nicely to exit. The nearly canonical approach to doing that is as follows: class MyThread(threading.Thread): def __init__(self, *args, **kwargs): threading.Thread.__init__(self, *args, **kwargs) self._keepRunning = True def stop(self, timeout=None): self._keepRunning = False # optional: wait for thread to exit self.join(timeout=timeout) def run(self): while self._keepRunning: # do stuff here Now you can do things like this: thread = MyThread() thread.start() # other stuff... thread.stop()# block here until the thread exits I hope that clarifies things a little more... -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Op 2005-10-18, dcrespo schreef [EMAIL PROTECTED]: Before, after, or during the .start() call, or somewhere else? I'd like to catch *just after* the .start() call. I'm quite sure the problem you are trying to solve can be solved, but you are still describing part of the solution you believe you need, rather than explaining why you want to do this (which may let us show you other, simpler or cleaner ways to accomplish your goals). The thing is that I have in ProgramB a class derived from threading.Thread, that runs a TCPServer, listening to a port on local ip address. As you surely know, you have to specify certain parameters when instantiating the tcpserver: SocketServer.TCPServer(server_address, RequestHandlerClass) where server_address is a tuple (ip,port) ip has to be one of three modes of values (If I remember well): 1. A null string '' Listens on all IP local address 2. A string containing the local IP address where you want it to listen Listens only in the specified local IP address 3. A string containing localhost. Listens only for connections from localhost. Here comes the problem: When you specify the case number 2, the IP must be valid for the computer where the program runs, otherwise, it raises an exception saying that Can't assign requested address. The TCPServer class, defined in a module, is ran (instantiatedly) from the main program through a started thread. The thread also is in the same module as TCPServer class. It looks like (it's much more code than this. If you want the whole code, tell me): MainProgram.py ... SrvrTCP = module.ThreadedTCPServer(ip,port) SrvrTCP.start() #Here, I want to know if the TCPServer started well. ... module.py ... class ThreadedTCPServer(threading.Thread): def __init__(self, ip,port): threading.Thread.__init__(self) self.ip= ip self.port= port def run(self): TCPServer((self.ip,self.port)) #Here, if the self.ip is invalid, it raises an exception. Just a suggestion, but since it is the main thread you want notified, you could use signals here. Something like the following: MainProgram.py class TCPProblem(Exception): pass def signalcallback(signum, frame): raise TCPProblem signal.signal(signal.SIGHUP, signalcallback) SrvrTCP = module.ThreadedTCPServer(ip,port) SrvrTCP.start() ... module.py mainpid = os.getpid() class ThreadedTCPServer(threading.Thread): def __init__(self, ip,port): threading.Thread.__init__(self) self.ip= ip self.port= port def run(self): try: TCPServer((self.ip,self.port)) #Here, if the self.ip is invalid, it raises an exception. except ...: os.kill(mainpid, signal.SIGHUP) -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Now that may not be perfect, since I'm not familiar with the TCPServer() call. I've sort of assumed it does something quickly and returns, or raises an exception if the input is bad. If it doesn't actually return if it starts successfully, you would need a little different approach. Probably adding a simple timeout to the self.startEvent.wait() call would work. It's perfect! Thank you very much. After the .start() call in the main thread, it just waits until was a succesfull thread start. It's just perfect. One more thing, I would like to catch the description string of the error, so I can show it to the user in a Message Box. How can I do that in the main threa, once that I allready catched the exception? Thank you so much -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Ok, sorry about the above question. I solved it adding this to the main thread: try: SrvrTCP = module.ThreadedTCPServer(ip,port) SrvrTCP.start() except Exception, description: MsgBox(self,TCPServer Error:\n\n+str(description),title=TCPServer,style=wx.OK | wx.ICON_ERROR) return Peter, thank you very much. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Before, after, or during the .start() call, or somewhere else? I'd like to catch *just after* the .start() call. I'm quite sure the problem you are trying to solve can be solved, but you are still describing part of the solution you believe you need, rather than explaining why you want to do this (which may let us show you other, simpler or cleaner ways to accomplish your goals). The thing is that I have in ProgramB a class derived from threading.Thread, that runs a TCPServer, listening to a port on local ip address. As you surely know, you have to specify certain parameters when instantiating the tcpserver: SocketServer.TCPServer(server_address, RequestHandlerClass) where server_address is a tuple (ip,port) ip has to be one of three modes of values (If I remember well): 1. A null string '' Listens on all IP local address 2. A string containing the local IP address where you want it to listen Listens only in the specified local IP address 3. A string containing localhost. Listens only for connections from localhost. Here comes the problem: When you specify the case number 2, the IP must be valid for the computer where the program runs, otherwise, it raises an exception saying that Can't assign requested address. The TCPServer class, defined in a module, is ran (instantiatedly) from the main program through a started thread. The thread also is in the same module as TCPServer class. It looks like (it's much more code than this. If you want the whole code, tell me): MainProgram.py ... SrvrTCP = module.ThreadedTCPServer(ip,port) SrvrTCP.start() #Here, I want to know if the TCPServer started well. ... module.py ... class ThreadedTCPServer(threading.Thread): def __init__(self, ip,port): threading.Thread.__init__(self) self.ip= ip self.port= port def run(self): TCPServer((self.ip,self.port)) #Here, if the self.ip is invalid, it raises an exception. ... -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
dcrespo wrote: Before, after, or during the .start() call, or somewhere else? I'd like to catch *just after* the .start() call. Excellent. That makes it pretty easy then, since even though you are spawning a thread to do the work, your main thread isn't expected to continue processing in parallel. See my draft solution below. If it doesn't seem to suit, explain where it fails you and we can try to evolve it (assuming we're on the same page at all here). When you specify the case number 2, the IP must be valid for the computer where the program runs, otherwise, it raises an exception saying that Can't assign requested address. MainProgram.py ... SrvrTCP = module.ThreadedTCPServer(ip,port) SrvrTCP.start() #Here, I want to know if the TCPServer started well. Leave that part as it is. We'll override the start() method in your subclass to solve your problem. module.py ... class ThreadedTCPServer(threading.Thread): def __init__(self, ip,port): threading.Thread.__init__(self) self.ip= ip self.port= port self.startError = None self.startedEvent = threading.Event() def start(self): '''start thread and wait for successful start''' threading.Thread.start(self) self.startedEvent.wait() if self.startError: raise self.startError def run(self): TCPServer((self.ip,self.port)) #Here, if the self.ip is invalid, it raises an exception. ... We have to change the run() method slightly now: def run(self): try: try: TCPServer((self.ip, self.port)) except Exception, ex: self.startError = ex return finally: self.startedEvent.set() # do the rest of the existing run() code here Now that may not be perfect, since I'm not familiar with the TCPServer() call. I've sort of assumed it does something quickly and returns, or raises an exception if the input is bad. If it doesn't actually return if it starts successfully, you would need a little different approach. Probably adding a simple timeout to the self.startEvent.wait() call would work. Note also that you don't get the full original traceback with this technique. I'm not sure you can, actually (though I can imagine that with Python one could stitch together a traceback from a previous exception as one raises a new exception). From what you describe, however, it sounds like you just need to know that the exception occurred, not the precise line of code down in TCPServer() where it was originally raised. I hope that helps and/or gives you some leads on a better solution. -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
[EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. Definitely a better architecture. Anyway, one supported way for a thread to raise an exception in a different thread is function thread.interrupt_main(), which raises a KeyboardInterrupt in the *main* thread (the one thread that's running at the beginning of your program). There's also a supported, documented function to raise any given exception in any existing thread, but it's deliberately NOT directly exposed to Python code -- you need a few lines of C-coded extension (or pyrex, ctypes, etc, etc) to get at the functionality. This small but non-null amount of attrition was deliberately put there to avoid casual overuse of a facility intended only to help in very peculiar cases (essentially in debuggers c, where the thread's code may be buggy and fail to check a keep-alive flag correctly...!-). Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Op 2005-10-14, dcrespo schreef [EMAIL PROTECTED]: Hi all, How can I get a raised exception from other thread that is in an imported module? For example: You could try the following class, it needs ctypes and if the exception is raised while in a C-extention, the exception will be delayed until the extention is left. Some delay is unavoidable. You may also need to fiddle with the length of the sleep at the end of this script or the values in the xrange calls in the Continue threads except.py import os import ctypes from time import sleep from random import randint class TimeOut(Exception): pass class Alarm(Exception): pass import threading class Xthread(threading.Thread): def start(self): self.__original_run = self.run self.run = self.__run threading.Thread.start(self) def __run(self): self.__thrd_id = threading._get_ident() try: self.__original_run() finally: self.run = self.__original_run def raize(self, excpt): Nr = ctypes.pythonapi.PyThreadState_SetAsyncExc(self.__thrd_id, ctypes.py_object(excpt)) while Nr 1: ctypes.pythonapi.PyThreadState_SetAsyncExc(self.__thrd_id, None) sleep(0.1) Nr = ctypes.pythonapi.PyThreadState_SetAsyncExc(self.__thrd_id, ctypes.py_object(excpt)) def alarm(self, tm): alrm = threading.Timer(tm, self.raize, (TimeOut,)) alrm.start() return alrm class Continue(Xthread): def run(self): self.id = os.getpid() print self.id, Begin i = 0 try: for _ in xrange(randint(0,20)): for e in xrange(4 * 10): i = i + e print self.id, Finished except Alarm: print self.id, Interupted lst = [Continue() for _ in xrange(10)] for T in lst: T.start() try: sleep(15) finally: for T in lst: T.raize(Alarm) -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Op 2005-10-17, Alex Martelli schreef [EMAIL PROTECTED]: [EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. Definitely a better architecture. Anyway, one supported way for a thread to raise an exception in a different thread is function thread.interrupt_main(), which raises a KeyboardInterrupt in the *main* thread (the one thread that's running at the beginning of your program). There's also a supported, documented function to raise any given exception in any existing thread, but it's deliberately NOT directly exposed to Python code -- you need a few lines of C-coded extension (or pyrex, ctypes, etc, etc) to get at the functionality. This small but non-null amount of attrition was deliberately put there to avoid casual overuse of a facility intended only to help in very peculiar cases (essentially in debuggers c, where the thread's code may be buggy and fail to check a keep-alive flag correctly...!-). I find this rather arrogant. It is not up to the developers of python to decide how the users of python will use the language. If someone has use of specific functionality he shouldn't be stopped because his use is outside the intentions of the developers. Just suppose you are writing a chess program. You let the program think while it is the users move, but this thinking has to be interrupted and some cleanup has to be made after the users move has made a lot of this thinking obsolete by his move. Such code could be mixture of loops and recursion that makes use of a simple flag to end it all, unpractical. Use of an exception raised from somewhere else would IMO in this case be an acceptable choice. Why should the coder of this software have to go through this deliberate set up attrition, to get at this functionality, just because it wasn't intented to be used in such a way by the developers? As far as I know, pyrex and ctypes weren't intended to get at the Python/C api. But they didn't create extra hurdles for those who could use it that way. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Antoon Pardon wrote: Op 2005-10-17, Alex Martelli schreef [EMAIL PROTECTED]: [EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. Definitely a better architecture. Anyway, one supported way for a thread to raise an exception in a different thread is function thread.interrupt_main(), which raises a KeyboardInterrupt in the *main* thread (the one thread that's running at the beginning of your program). There's also a supported, documented function to raise any given exception in any existing thread, but it's deliberately NOT directly exposed to Python code -- you need a few lines of C-coded extension (or pyrex, ctypes, etc, etc) to get at the functionality. This small but non-null amount of attrition was deliberately put there to avoid casual overuse of a facility intended only to help in very peculiar cases (essentially in debuggers c, where the thread's code may be buggy and fail to check a keep-alive flag correctly...!-). I find this rather arrogant. It is not up to the developers of python to decide how the users of python will use the language. If someone has use of specific functionality he shouldn't be stopped because his use is outside the intentions of the developers. The developers have to support (at no cost) what the users do, so if they want to make use of certain features inaccessible to users who are likely to go wrong then that's up to them. Just suppose you are writing a chess program. You let the program think while it is the users move, but this thinking has to be interrupted and some cleanup has to be made after the users move has made a lot of this thinking obsolete by his move. Such code could be mixture of loops and recursion that makes use of a simple flag to end it all, unpractical. Use of an exception raised from somewhere else would IMO in this case be an acceptable choice. In *your* opinion, possibly. In my opinion it would seem to make more sense to have the worker thread code examine a shared flag and raise an exception at some convenient point in its calculation cycle. Otherwise you have to write the worker thread to be capable of handling asynchronous signals, which is a notoriously difficult task. I presume this is why Alex commented that he thought the OP's better solution was definitely a better architecture. Why should the coder of this software have to go through this deliberate set up attrition, to get at this functionality, just because it wasn't intented to be used in such a way by the developers? Because otherwise people who know no better will use the feature for purposes where it's not the best way to achieve the required functionality, leading to yet more endless discussions about why it doesn't work. Asynchronous signalling between threads is an accident waiting to happen in the hands of an inexperienced programmer. As far as I know, pyrex and ctypes weren't intended to get at the Python/C api. But they didn't create extra hurdles for those who could use it that way. This seems like a complete non sequitur to me. Let's stick to the point. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Steve Holden [EMAIL PROTECTED] writes: Otherwise you have to write the worker thread to be capable of handling asynchronous signals, which is a notoriously difficult task. Doing it properly needs a language extension. http://www.cs.williams.edu/~freund/papers/02-lwl2.ps -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Op 2005-10-17, Steve Holden schreef [EMAIL PROTECTED]: Antoon Pardon wrote: Op 2005-10-17, Alex Martelli schreef [EMAIL PROTECTED]: [EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. Definitely a better architecture. Anyway, one supported way for a thread to raise an exception in a different thread is function thread.interrupt_main(), which raises a KeyboardInterrupt in the *main* thread (the one thread that's running at the beginning of your program). There's also a supported, documented function to raise any given exception in any existing thread, but it's deliberately NOT directly exposed to Python code -- you need a few lines of C-coded extension (or pyrex, ctypes, etc, etc) to get at the functionality. This small but non-null amount of attrition was deliberately put there to avoid casual overuse of a facility intended only to help in very peculiar cases (essentially in debuggers c, where the thread's code may be buggy and fail to check a keep-alive flag correctly...!-). I find this rather arrogant. It is not up to the developers of python to decide how the users of python will use the language. If someone has use of specific functionality he shouldn't be stopped because his use is outside the intentions of the developers. The developers have to support (at no cost) what the users do, Only in so far that correct programs behave correctly. The developers are not obligated to correct buggy programs. They have every right to say that if a programmor can handle certain concepts he should seek help with that concept elsewhere. so if they want to make use of certain features inaccessible to users who are likely to go wrong then that's up to them. But the way it is made inaccessible has nothing to do with knowing how to use the feature. That you can dable with C-extententions, pyrex or ctypes says nothing about your ability to handle threads that raise exceptions in each other. Just suppose you are writing a chess program. You let the program think while it is the users move, but this thinking has to be interrupted and some cleanup has to be made after the users move has made a lot of this thinking obsolete by his move. Such code could be mixture of loops and recursion that makes use of a simple flag to end it all, unpractical. Use of an exception raised from somewhere else would IMO in this case be an acceptable choice. In *your* opinion, possibly. In my opinion it would seem to make more sense to have the worker thread code examine a shared flag and raise an exception at some convenient point in its calculation cycle. What it there is no such convenient point? What if you have a number of differnt routines that recursively call each other each with its own number of nested loops. If you want something that is a bit responsive you will have to put a check for this flag in any loop. Otherwise you have to write the worker thread to be capable of handling asynchronous signals, which is a notoriously difficult task. I presume this is why Alex commented that he thought the OP's better solution was definitely a better architecture. IMO the flag is the better architecture in this case because python can't interrupt a tread with an exception while that thread is in C-code. Why should the coder of this software have to go through this deliberate set up attrition, to get at this functionality, just because it wasn't intented to be used in such a way by the developers? Because otherwise people who know no better will use the feature for purposes where it's not the best way to achieve the required functionality, leading to yet more endless discussions about why it doesn't work. Then don't react to those questions. A lot of questions about threads are already answered as follows: Don't use threads, use twised or If you have to use threads, use Queues. IMO there is nothing wrong with telling people that if they want to use certain features it is expected they know what thet are doing. Asynchronous signalling between threads is an accident waiting to happen in the hands of an inexperienced programmer. So? Do we want python to be limited to features that can't cause problems in the hands of an inexperienced programmer? -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Steve Holden wrote: snip Why should the coder of this software have to go through this deliberate set up attrition, to get at this functionality, just because it wasn't intented to be used in such a way by the developers? Because otherwise people who know no better will use the feature for purposes where it's not the best way to achieve the required functionality, leading to yet more endless discussions about why it doesn't work. Asynchronous signalling between threads is an accident waiting to happen in the hands of an inexperienced programmer. I can't agree with that opinion. There's tons of features of existing programming languages and systems, Python included, that is pretty much guaranteed to be misused, and badly at that. We can't remove those just on the off chance someone might start a thread on a newsgroup about why this is or isn't the best way to do things. If we do that then I guess list comprehension is out the window because there's tons of posts (from me included) that get this wrong. The point of a programming language is not to dumb down the environment to a point where it is impossible to write bad code. Instead it's about empowering the programmers to be able to accomplish their tasks. In any case, this exception-in-another-thread problem has inherent issues which must be solved, among others: - C extension code can't be interrupted - an exception thrown at the wrong time in a finally/except block might cause more problems than it intends to solve So until a good implementation exists, there shouldn't be any point in actually discussing the motives of the programmers who wishes to use the feature. snip -- Lasse Vågsæther Karlsen http://usinglvkblog.blogspot.com/ mailto:[EMAIL PROTECTED] PGP KeyID: 0x2A42A1C2 -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Hi Peter. Sorry for my delay. I wasn't in home the weekend. Define what get means for your purposes. It appears that you mean you want to catch the exception, but in the thread which launched the other thread in the first place. If that's true, please show where you would expect to catch this exception, given that when you start the thread, the main thread continues running and might even finish before the other thread finishes. In my above example, I want to catch in ProgramA the raised exception in ProgramB. Please, look at my example one more time. Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
dcrespo wrote: Define what get means for your purposes. It appears that you mean you want to catch the exception, but in the thread which launched the other thread in the first place. If that's true, please show where you would expect to catch this exception, given that when you start the thread, the main thread continues running and might even finish before the other thread finishes. In my above example, I want to catch in ProgramA the raised exception in ProgramB. Better not to call them programs since they're not separate programs, just separate modules, one of which starts a thread using methods in the other module. And you haven't really answered the questions I asked. Please show exactly where you expect to catch the exception, given the points I note above. Before, after, or during the .start() call, or somewhere else? Please, look at my example one more time. Done. It didn't really help looking at it a third time. It's still unclear what you want. Maybe explaining the use case would help you help us help you. :-) Your example seems contrived. In the real code you want to write, why do you expect an exception to occur? Will it be raised deliberately, as you show in the example, or is it unexpected (and unhandled by any try/except at the top level of the thread's run() method)? Or do you really need to use an exception here? I'm quite sure the problem you are trying to solve can be solved, but you are still describing part of the solution you believe you need, rather than explaining why you want to do this (which may let us show you other, simpler or cleaner ways to accomplish your goals). -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
In article [EMAIL PROTECTED], [EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. Thanx for all the input. How about a threading.Event? -Mike -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
[EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. As Dennis points out, your original attempt was destined to fail because you were calling the method from the main thread, not the one you wanted to kill. Threads don't magically execute any methods that are attached to the Thread instance just because they're attached. You have to actually call those methods *from* the thread, which means from the run() method or from any of the routines it calls (whether they are methods on that Thread or not), but it must be done in the context of the thread you want to raise exceptions in or it won't work. More importantly, you've now described your use case (and I hope that of the OP as well, since he hasn't replied yet): killing threads. This is an oft-discussed topic here, and searching the archives will probably give you lots more answers, but the short answer is you cannot kill a thread in Python (except by exiting the entire process). Instead, as you've discovered, you must ask it nicely to exit. The nearly canonical approach to doing that is as follows: class MyThread(threading.Thread): def __init__(self, *args, **kwargs): threading.Thread.__init__(self, *args, **kwargs) self._keepRunning = True def stop(self, timeout=None): self._keepRunning = False # optional: wait for thread to exit self.join(timeout=timeout) def run(self): while self._keepRunning: # do stuff here Now you can do things like this: thread = MyThread() thread.start() # other stuff... thread.stop()# block here until the thread exits I hope that clarifies things a little more... -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Peter Hansen wrote: [EMAIL PROTECTED] wrote: Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. As Dennis points out, your original attempt was destined to fail because you were calling the method from the main thread, not the one you wanted snip A similar problem exists in .NET but they solved it by creating an Abort method that raises an exception in the thread itself, basically doing what you wanted to do. However, this leads to all sorts of problem, particular when that exception is raised in a finally block in that thread, which could mean that the finally block did not fully execute, leading to resource leaks or similar problems. They pondered a while about constructing non-interruptible blocks of code for .NET 2.0 but I'm not entirely sure how that worked out. In any case, the best way is to use some kind of signal that the thread reacts to, either by having it specifically wait for a signallable object (like an event) or just by checking a boolean variable or similar for a magic value that means now is a good time for you to terminate. -- Lasse Vågsæther Karlsen http://usinglvkblog.blogspot.com/ mailto:[EMAIL PROTECTED] PGP KeyID: 0x2A42A1C2 -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Thanks for your answer, but I think that created thread in python should create a thread either on windows and linux. Can you give me Python example of how to do what I want to do? Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
dcrespo wrote: How can I get a raised exception from other thread that is in an imported module? Define what get means for your purposes. It appears that you mean you want to catch the exception, but in the thread which launched the other thread in the first place. If that's true, please show where you would expect to catch this exception, given that when you start the thread, the main thread continues running and might even finish before the other thread finishes. thread = programB.MakeThread() thread.start() ... # later code which might have completed by the time the thread finishes ... Are you looking, for example, for some kind of thread.waitUntilCompletionAndReRaiseExceptions() method? -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
I also need an answer to this problem. I'm using windows. Throwing an exception in thread B from thread A using a callback function. The function runs, but the thread never actually catches the exception. The try/except block is in the run() method (over-riden from the Thread class) -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
[EMAIL PROTECTED] wrote: I also need an answer to this problem. What _is_ the problem? We're still waiting for a clear description from the OP as to what the problem really is. How would you describe what _your_ problem is? I'm using windows. Throwing an exception in thread B from thread A using a callback function. The function runs, but the thread never actually catches the exception. The try/except block is in the run() method (over-riden from the Thread class) Rather than force us all to guess what you are doing wrong, maybe it would be better if you posted a small amount of code that shows the problem. Exceptions raised in threads can definitely be caught in the run() method if the code is written correctly, so that is not in itself an issue. -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Here's a dumbed down version of what i'm doing: import time import threading class threader(threading.Thread): def __init__(self): threading.Thread.__init__(self) pass def run(self): try: while 1: time.sleep(5) except SystemExit: print Got Exit Message in thread def killMe(self): raise SystemExit thread1 = threader() thread2 = threader() thread1.start() thread2.start() time.sleep(5) try: print Killing thread 1 thread1.killMe() print killing thread 2 thread2.killMe() except SystemExit: print Got exceptin in main thread The exception is not propogated to the threads I spawned, but instead comes back in the main thread. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Nevermind. I found a better solution. I used shared memory to create a keep-alive flag. I then use the select function with a specified timeout, and recheck the keep-alive flag after each timeout. Thanx for all the input. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
On non-Windows system there are a ton of ways to do it--this is almost a whole field unto itself. :) (D-BUS, fifos, sockets, shmfs, etc.) In Windows, I wouldn't have a clue. I guess this is a hard question to answer without a bit more information. :) On Fri, 2005-10-14 at 14:45 -0700, dcrespo wrote: Hi all, How can I get a raised exception from other thread that is in an imported module? For example: --- programA.py --- import programB thread = programB.MakeThread() thread.start() --- programB.py --- import threading, time class SomeException(Exception): pass class MakeThread(threading.Thread): def __init__(self): threading.Thread.__init__(self) def run(self): i = 0 while 1: print i i += 1 time.sleep(1) #wait a second to continue if i10: raise SomeException() Thanks Daniel -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a raised exception from other thread
Threads can share the same memory space. Hence a very neat way to achieve the objective. For example: --- programA.py --- import programB Exception=0;initialising a variable thread = programB.MakeThread() thread.start() if (Exception): raise SomeException() --- programB.py --- import threading, time class SomeException(Exception): pass class MakeThread(threading.Thread): def __init__(self): threading.Thread.__init__(self) def run(self): i = 0 while 1: print i i += 1 time.sleep(1) #wait a second to continue if i10:omit this -raise SomeException() instead: if i10: Exception=1 or whatever Sounds cool? shitizJeremy Moles [EMAIL PROTECTED] wrote: On non-Windows system there are a ton of ways to do it--this is almost awhole field unto itself. :) (D-BUS, fifos, sockets, shmfs, etc.) InWindows, I wouldn't have a clue. I guess this is a hard question to answer without a bit moreinformation. :)On Fri, 2005-10-14 at 14:45 -0700, dcrespo wrote: Hi all, How can I get a raised exception from other thread that is in an imported module? For example: --- programA.py --- import programB thread = programB.MakeThread() thread.start() --- programB.py --- import threading, time class SomeException(Exception): pass class MakeThread(threading.Thread):! ; def __init__(self): threading.Thread.__init__(self) def run(self): i = 0 while 1: print i i += 1 time.sleep(1) #wait a second to continue if i10: raise SomeException() Thanks Daniel -- http://mail.python.org/mailman/listinfo/python-list Yahoo! Music Unlimited - Access over 1 million songs. Try it free.-- http://mail.python.org/mailman/listinfo/python-list
