python-multithreading

问题 I am trying to run a certain function "foo" every second. I have to do this for a few minutes (say 5). The function foo() makes 100 HTTP Requests (which contains a JSON object) to the server and prints the JSON response. In short, I have to make 100 HTTP requests per second for 5 minutes. I have just started learning python, thus don't have extensive knowledge. This is what I have tried: import threading noOfSecondsPassed = 0 def foo(): global noOfSecondsPassed # piece of code which makes 100

问题 This question already has answers here : Threading Best Practices (11 answers) Closed 6 years ago . i have a question regards python locks and threading, i realise locks are used to prevent variables from being overwritten by another thread, is it normal to use locks to get around this issue as it then means you can only run a single thread concurrently, it also means creating acquire/release locks for every variable that maybe overwritten, which for my project runs into quite a few! how are

问题 I have a function, let's call it my_function(*args, **kwargs) , that depending on the arguments passed to it takes anywhere from 30 seconds to many many hours (days). I have a list of different arguments and I want to know how long the functions will take given the arguments. I am still very new to using timeit , but I have learn enough to do this part; however, this wouldn't be the very efficient for my purposes. Any set of arguments that take longer than 4 hours to complete are consider

问题 I was using threading module with OpenCV, I came accross a bizarre issue. When using thread I was unable to start the camera again to take video input. I would take one frame and then stop. While there was no problem like this when using multiprocessing module. I am unable to understand what causes this strange behaviour. This code summarizes the problem I have, The program will stuck when the thread is created second time. import cv2 import time import threading def open_cam(): count = 0 cam

问题 I would like to understand why I must wait for my receiver thread to end its work before I can do anything else. I understand that my sock_listen function is awaiting a connection, that's what its meant for, but I don't understand why this isn't happening "within" my thread. Sorry if this is a stupid question but I'm kind of lost ! Thank you in advance! def sock_listen(address, port): sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_address = (address,port) print("Starting

问题 Let's say I have a web bot written in python that sends data via POST request to a web site. The data is pulled from a text file line by line and passed into an array. Currently, I'm testing each element in the array through a simple for-loop. How can I effectively implement multi-threading to iterate through the data quicker. Let's say the text file is fairly large. Would attaching a thread to each request be smart? What do you think the best approach to this would be? with open("c:\file.txt

问题 I'm trying to understand how to implement a Queue with a bounded buffer size that can be used by multiple producers and consumers using Python Semaphores. Here's my implementation: class Q: def __init__(self, size): self.buff = [None]*size self.end = 0 self.start = 0 self.size = size self.end_lock = Lock() # protect end from race across multiple producers self.start_lock = Lock() # protect start from race across multiple consumers self.open = Semaphore(size) # block till there's space to

问题 The code below works fine. I can't find a way to pass some arguments to EventHandler or to call methods of MainClass from EventHandler . For example instead of using constant param , I'd like to pass it through constructor or setter method. I've tried recommendations from here. But in this case EventHandler instance does not catch any events (or at least nothing appears in stdout). class EventHandler: param = "value" def OnConnected(self): print 'connected' return True class MainClass: def

问题 Forgive me if this has been asked before. I have looked around a lot, but I get the feeling that I don't have the proper vocabulary to find this by searching the web. I have a multithreaded application in python. I want to be able to lock a certain block of code but only to other threads with a certain condition. Let me give an example: There are three threads, thread_a , thread_b and thread_c . Each thread may run through the function foo at any time. I don't want any two threads with bar

问题 I have a shared global data object in my single-process multi-threaded django server - an object which is frequently used, but calculated infrequently. The calculation is time-consuming, so I want to share the results. I thought it would work to use django's LocalMemCache for this simple data. Oddly, it seems to work for multiple ajax calls on a single page load, but for some reason, when I reload the page in my browser, the cache is empty again. What am I doing wrong? Is there a better way?