multithreading - QThread use in Python -


i new in writing bigger programs in python (i writing short scripts before). program i'm write recives data external device, saves database , displays in gui (continuously). since handling data time consuming want use threads (pyside qtcore qthreads specific). best way can think of set 2 threads, 1 database processes , 1 handling of serial port, gui running in mainthread. i've read whole bunch of stuff proper/improper qthreading, starting maya's post , digging deeper, this post found that:

when subclass , when not to?

if not need event loop in thread, should subclass. if need event loop , handle signals , slots within thread, may not need subclass.

question 1: first thing don't know way go (subclassing or not). guess subclassing, since (question2), i'm not entirely sure , i'm sticking movetothread().

question 2: other thing have no clue how make actions in threads event-driven (the serialthread receives data device, sends via signal databasethread, databasethread collects data , puts in database).

question 3: when using movetothread() attributeerror: 'pyside.qtcore.qthread' object has no attribute 'my_awesome_method' every method write class. it's clear me don't understand principle of operation here. how implement methods want my_class have while using my_class.movetothread(my_thread)?

i've found tutorials possible on qthreads , c++, discussion on qthreads in python interesting, not explain want know. need simple example signals, slots , exact explanation on how use run(). decorate it? why? how? how work?

the short version of code looks this:

from pyside import qtcore app.thrads.gui.gui import gui            #my own class app.threads.db.db import database        #my own class app.threads.serial.serial import serial  #my own class  class appmanager():     def __init__(self):         self.gui = gui()          self.db = database()         self.db_thread = qtcore.qthread()         self.db.movetothread(self.db_thread)         self.db_thread.start()          self.serial = serial()         self.serial_thread = qtcore.qthread()         self.serial.movetothread(self.serial_thread)         self.serial_thread.start()

and database , serial class this:

from pyside import qtcore .db_signal import dbsignal  class database(qtcore.qobject):     def __init__(self):         super(database, self).__init__()         self.signal = dbsignal()      def my_awesome_method(self):         ''' awesome '''         pass

question 1

i think best way easiest: don't subclass, create 2 different threads. in first, move database object, in second serial one. it, won't make mistakes in implementation of sub-classed threads,and bug fixing quicker.

question 2

i don't know architecture of application, follows, after creating threads , moving worker objects in them:

self.serial_thread.started.connect(self.serial.start) self.serial_thread.finished.connect(self.serial.stop)  self.db_thread.started.connect(self.db.start) self.serial_thread.finished.connect(self.db.stop)  self.serial.data_ready.connect(self.db.handle_new_data)  # starting database first, won't lose single packet of data self.db_thread.start() self.serial_thread.start()

in fact, advantage of qthreads doesn't modify code.

question 3

i think problem you're trying call my_awesome_method qthread data base or serial listener has been moved to. on contrary, should call method object itself, if wasn't in different thread !

# bad! obj.movetothread(thread) thread.method_of_obj(param)  # good! obj.movetothread(thread) obj.method_of_obj(param)

Comments

Post a Comment

Popular posts from this blog

php - failed to open stream: HTTP request failed! HTTP/1.0 400 Bad Request -

this code i'm using find latitude , longitude of place: function coords($address){ echo $url="http://maps.googleapis.com/maps/api/geocode/json?address=".$address; $json = file_get_contents(urlencode($url)); $data = json_decode($json, true); print_r($data['results'][0]['geometry']['location']['lat']); print_r($data['results'][0]['geometry']['location']['lng']); } however returns warning: failed open stream: http request failed! http/1.0 400 bad request if use above code in simple procedure works fine not in function. note: have tried curl_init()... method produced same result? instead of encoding whole url encode address part. following code work fine $add='jamshoro phase 2'; $url="http://maps.googleapis.com/maps/api/geocode/json?address=".urlencode($add); $json = file_get_contents($url); $data = json_decode($json, true); print_r($data['r
Read more

java - How to filter a backspace keyboard input -

i have code gives message when key number pressed: txtvalueofclause.addeventfilter(keyevent.key_typed, new eventhandler<keyevent>() { @override public void handle(keyevent t) { char ar[] = t.getcharacter().tochararray(); char ch = ar[t.getcharacter().tochararray().length - 1]; if (!(ch >= '0' && ch <= '9')) { system.out.println("the char entered not number"); t.consume(); } } }); now if press on wrong button , press backspace remove it, error message. how can add backspace input if statement? i have found answer: txtvalueofclause.addeventfilter(keyevent.key_typed, new eventhandler<keyevent>() { @override public void handle(keyevent t) { char ar[] = t.getcharacter().tochararray(); char ch = ar[t.getcharacter().tochar
Read more

java - Show Soft Keyboard when EditText Appears -

i have code in android app, alert dialog , keyboard, , when dialog shown want keyboard appear. not , not sure why? here code: final alertdialog.builder alert = new alertdialog.builder(this); alert.settitle("title"); alert.setmessage("message"); final edittext input = new edittext(this); input.setinputtype(inputtype.type_class_number); alert.setview(input); input.setonfocuschangelistener(new view.onfocuschangelistener() { @override public void onfocuschange(view v, boolean hasfocus) { if (hasfocus) { log.i(tag, "in focus"); inputmethodmanager inputmethodmanager = (inputmethodmanager) getsystemservice(context.input_method_service); inputmethodmanager.showsoftinput(input, inputmethodmanager.show_implicit); } } }); but keyboard not appear though edit text in focus, , tell appear why, doesn't come up? thanks in advance.
Read more