multithreading

问题 I have just started with Python, although I have been programming in other languages over the past 30 years. I wanted to keep my first application simple, so I started out with a little home automation project hosted on a Raspberry Pi. I got my code to work fine (controlling a valve, reading a flow sensor and showing some data on a display), but when I wanted to add some web interactivity it came to a sudden halt. Most articles I have found on the subject suggest to use the Flask framework to

问题 Python guru I need your help. I faced quite strange behavior: empty python Process hangs on joining . Looks like it forks some locked resource. Env: Python version: 3.5.3 OS: Ubuntu 16.04.2 LTS Kernel: 4.4.0-75-generic Problem description: 1) I have a logger with thread to handle messages in background and queue for this thread. Logger source code (a little bit simplified). 2) And I have a simple script which uses my logger (just code to display my problem): import os from multiprocessing

问题 I have just started with Python, although I have been programming in other languages over the past 30 years. I wanted to keep my first application simple, so I started out with a little home automation project hosted on a Raspberry Pi. I got my code to work fine (controlling a valve, reading a flow sensor and showing some data on a display), but when I wanted to add some web interactivity it came to a sudden halt. Most articles I have found on the subject suggest to use the Flask framework to

问题 I am trying to create a new thread gpsthread which should run in the back ground, and store the value. class gpsthread: public QThread{ Q_OBJECT private:nrega_status_t status2; public: explicit gpsthread(QObject *parent = 0):QThread(parent) { // QTimer *t = new QTimer(this); // connect(t, SIGNAL(timeout()), this, SLOT(processgps())); // t->start(10000); } void run(){ qDebug()<<"inside gps thread\n"; QTimer *t = new QTimer(this); connect(t, SIGNAL(timeout()), this, SLOT(processgps())); t-

问题 I've read that the UI should always be updated on the main thread. However, I'm a little confused when it comes to the preferred method to implement these updates. I have various functions that perform some conditional checks then the result is used to determine how to update the UI. My question is should the entire function run on the main thread? Should just the UI update? Can / should I run the conditional checks on another thread? Does it depend on what the function does or how fast you

问题 This question already has answers here : Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on (22 answers) Closed 4 years ago . I have a Windows form which is taking forever to load data into my datagridview. I keep getting the error in this line: dataGridView1.Rows.Add(row); Cross-thread operation not valid: Control 'dataGridView1' accessed from a thread other than the thread it was created on. Here is my code: public List<string> _checked

问题 Is it true that threads, compared to processes, are less likely to benefit from a multi-core processor? In other words, would the kernel make the decision of executing threads on a single core rather than on multiple cores? I'm talking about threads belonging to the same process. 回答1: I don't know how the (various) Linux scheduler handle this, but inter-thread communication gets more expensive when threads are running on different Cores. So the scheduler may decide to run threads of a process

问题 How can I send and receive messages between threads? 回答1: One solution would be share a concurrent queue, for example (albeit its name) ConcurrentQueue. This will allow you to enqueue an object from one thread and have the other thread (or others threads) dequeue from the queue. As it is a generic solution, you may pass strongly typed items, anything from string to Action will do, or your own custom message class of course. Threre is just one limitation with this approach, the class

问题 I read the following code in "Thinking in java". synchronized(obj) { while (condition_not_matched) { obj.wait(); } //continue dosomething(); } What I think: Use "if" is OK, because the "wait" means it must get the obj's lock monitor, and only one thread can executed here. (1)Why here use "while (condition)" not "if" ? (2)What happend when executed "obj.wait()"? Does the currrent thread release the lock of "obj"? (3)And when another thread executed "obj.notify()", what happend of the previous

问题 I read the following code in "Thinking in java". synchronized(obj) { while (condition_not_matched) { obj.wait(); } //continue dosomething(); } What I think: Use "if" is OK, because the "wait" means it must get the obj's lock monitor, and only one thread can executed here. (1)Why here use "while (condition)" not "if" ? (2)What happend when executed "obj.wait()"? Does the currrent thread release the lock of "obj"? (3)And when another thread executed "obj.notify()", what happend of the previous