- Python Pyqt Signals And Slot
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- Pyqt Signals And Slots
PyQt5 - Signal and slot function The signal and slot operation are used to handle events and signals of the objects or widgets at the python app development level. It will also enable communication between some designed objects. The following steps are needed for creating a Python signal and slot operations. PyQt5 signals and slots Graphical applications (GUI) are event-driven, unlike console or terminal applications. A users action like clicks a button or selecting an item in a list is called an event. If an event takes place, each PyQt5 widget can emit a signal.
Multithreading technology is used to design three methods, one is to use counter module QTimer, the other is to use multithreading module QThread, and the other is to use event processing function.
QTimer
If you want to perform an operation periodically in the application summary, such as periodically detecting the CPU of the host, you need to use the QTimer (timer). The QTimer class provides repetitive and single timers. To use the timer, you need to first create an instance of the QTImer, connect its timeout signal to the corresponding slot, and call start.
The demo pops up a window, which disappears after 10 seconds.
QThread
QThread is the core underlying class in Qt threads
Thread instances can be invoked directly when using threads, and threads can be started by calling its start() function. After starting threads, the run method implemented by threads can be invoked automatically. This method starts with the execution function of threads.
The thread task of the business is written in the run function, and the thread ends when run exits. QThread has strarted and finished signals. It can specify slot functions for these two signals, and specify a section of code to initialize and release resources after the start and end of the thread.
Common methods
- start
- wait
- sleep
Python Pyqt Signals And Slot
Although the interface data display and data read-write are separated, if the data read-write is very time-consuming, the interface will be stuck.
We use loops to simulate very time-consuming work. When the test button is clicked, the program interface stops responding directly. It is not updated until the end of the loop, and the timer is always displayed at 0.
All windows in PyQt are in the main thread of the UI, which blocks the UI thread by performing time-consuming operations, thus stopping the window from responding. If the window does not respond for a long time, it will affect the user experience. To avoid this problem, use the QThread to open a new thread to perform time-consuming operations on that thread.
WorkThread inherits from the QThread class and rewrites its run function. The run() function is what the new thread needs to execute. In the run function, a loop is executed, and then the calculated signal is transmitted.
event processing
PyQt uses two mechanisms for event handlers: high-level signal and slot mechanisms and low-level event handlers. We introduce the use of the low-level event handler, the processEvents() function, whose function is to process time, simply to refresh the page.
Golden lion casino panama eventos. For a time-consuming program, PyQt has to wait for the program to finish execution before it can proceed to the next step, which is shown as Katon on the page.
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Thinkpad t410 ram specs. Added by victor78 on Thu, 26 Sep 2019 10:33:26 +0300
While working on ape I had a problem with figuring out how to properly connect a signal to a slot, where the signal is emitted by a QTreeView widget. As this is not my first app with python and pyqt, I was doing something like (this is, btw, the 'old style'):
but it simply didn't work. Nothing happened. I was trying all different of connect/signal/slot combinations but everything was just dead silent. Google gave only pretty much old posts talking about QT3. Then I figured that, because the QTreeView is 'sitting' inside a QDockWidget, maybe that dock widget thingy is somehow intercepting/taking over the signals. Nope. Wth? Wtf is going on? Current pyqt version is (on my machine) 4.6. Last time I used pyqt it was something like 4.2 or 4.3. Something must've been changed in the mean time. Off to the pyqt docs I go (btw, I use the official QT docs, the C++ version, there isn't really a big difference from pyqt): PyQt reference, chapter 7 - 'New-style Signal and Slot Support'. A-ha! They changed it! Here is an example of the 'new style':
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Oh my, isn't that just beautiful?! Much more readable and simpler, for me at least. And it works! Yay! The QTreeView signals are happily connected to slots, thus, I'm happy too.
A few paragraphs later, turns out that the 'old style' isn't thrown out, it should still work. Why it didn't work for me escapes me at the moment, but honestly, I don't really care as long as the new style is working.
Pyqt Signals And Slots
Happy hackin'!
