python-multithreading

If I have an integer i , it is not safe to do i += 1 on multiple threads: >>> i = 0 >>> def increment_i(): ... global i ... for j in range(1000): i += 1 ... >>> threads = [threading.Thread(target=increment_i) for j in range(10)] >>> for thread in threads: thread.start() ... >>> for thread in threads: thread.join() ... >>> i 4858 # Not 10000 However, if I have a list l , it does seem safe to do l += [1] on multiple threads: >>> l = [] >>> def extend_l(): ... global l ... for j in range(1000): l += [1] ... >>> threads = [threading.Thread(target=extend_l) for j in range(10)] >>> for thread in

I have a VM as a server with IP address 10.91.55.2. I have another VM which acts as a client having IP address in the range 10.91.56.2......10.91.56.10. I want to write a script that will use all these IP address on the client to send HTTP request to the server (10.91.55.2). I have written a script that sends HTTP requests using the Physical IP address alone. Is there any way to send HTTP Requests from a range of IP address. My OS Is linux. Peter Gibson This is not a complete answer, but should provide you with a starting point. You say "I have another VM which acts as a client", so I'll

My app has the following structure: import tkinter as tk from threading import Thread class MyWindow(tk.Frame): ... # constructor, methods etc. def main(): window = MyWindow() Thread(target=window.mainloop).start() ... # repeatedly draw stuff on the window, no event handling, no interaction main() The app runs perfectly, but if I press the X (close) button, it closes the window, but does not stop the process, and sometimes even throws a TclError . What is the right way to write an app like this? How to write it in a thread-safe way or without threads? Main event loop should in main thread, and

Upon looking up event handler modules, I came across pydispatcher, which seemed beginner friendly. My use case for the library is that I want to send a signal if my queue size is over a threshold. The handler function can then start processing and removing items from the queue (and subsequently do a bulk insert into the database). I would like the handler function to run in the background. I am aware that I can simply overwrite the queue.append() method checking for the queue size and calling the handler function asynchronously, but I would like to implement the listener-dispatcher model to

I have an sqlite3 db that is being accessed concurrently. I have ClientA that reads the state of some table (Column1 has rows A , B , C ) and needs to update the table with new letters of the alphabet. If ClientB reads the state of the table before ClientA updates the table (say with the new letter D ), then it's possible that both clients could (and in my case do ) write D to the table - such that Column1 becomes A , B , C , D , D . But I need to ensure Column1 only has unique letters! How do I lock the db connection so that its read AND write operations get exclusive access so that Column1

I was able to improve a code written in python a lot with numpy because of the dot product. Now I still have one part of the code which is still very slow. I still don't understand multithreading and if this could help here. In my opinion this should be possible here. Do you have a nice idea what to do here? for x1 in range(a**l): for x2 in range(a**l): for x3 in range(a**l): f11 = 0 cv1 = numpy.ndarray.sum( numpy.absolute(numpy.subtract(ws[x1], ws[x2]))) cv2 = numpy.ndarray.sum( numpy.absolute(numpy.subtract(ws[x1], ws[x3]))) if cv1 == 0: f11 += 1 if cv2 == 0: f11 += 1 re[x1][x2][x3] = 1.0*r/