This object contains information about the event and can be used to respond differently depending on what exactly has occurred. We'll look at the mouse event objects next. All mouse events in Qt are tracked with the QMouseEvent object, with information about the event being readable from the following event methods.
You can use these methods within an event handler to respond to different events differently, or ignore them completely. The positional methods provide both global and local widget-relative position information as QPoint objects, while buttons are reported using the mouse button types from the Qt namespace. For example, the following allows us to respond differently to a left, right or middle click on the window.
On right-handed mice the left and right button positions are reversed, i. This means you don't need to account for the mouse orientation in your code. Context menus are small context-sensitive menus which typically appear when right clicking on a window. Qt has support for generating these menus, and widgets have a specific event used to trigger them. In the following example we're going to intercept the. This event is fired whenever a context menu is about to be shown, and is passed a single value event of type QContextMenuEvent.
To intercept the event, we simply override the object method with our new method of the same name. So in this case we can create a method on our MainWindow subclass with the name contextMenuEvent and it will receive all events of this type. If you run the above code and right-click within the window, you'll see a context menu appear.
You can set up. When passing the initial position to the exec function, this must be relative to the parent passed in while defining. In this case we pass self as the parent, so we can use the global position. In PyQt every widget is part of two distinct hierarchies: the Python object hierarchy, and the Qt layout hierarchy. How you respond or ignore events can affect how your UI behaves. Often you may want to intercept an event, do something with it, yet still trigger the default event handling behavior.
If your object is inherited from a standard widget, it will likely have sensible behavior implemented by default. You can trigger this by calling up to the parent implementation using super. This is the Python parent class, not the PyQt. When you add a widget to your application, it also gets another parent from the layout.
The parent of a widget can be found by calling. Sometimes you specify these parents manually, such as for QMenu or QDialog , often it is automatic. When you add a widget to your main window for example, the main window will become the widget's parent. When events are created for user interaction with the UI, these events are passed to the uppermost widget in the UI. So, if you have a button on a window, and click the button, the button will receive the event first. If the first widget cannot handle the event, or chooses not to, the event will bubble up to the parent widget, which will be given a turn.
This bubbling continues all the way up nested widgets, until the event is handled or it reaches the main window. In your own event handlers you can choose to mark an event as handled calling. Alternatively, you can mark it as unhandled by calling. In this case the event will continue to bubble up the hierarchy. If you want your widget to appear transparent to events, you can safely ignore events which you've actually responded to in some way. Similarly, you can choose to accept events you are not responding to in order to silence them.
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Still, if your app needs it, go 4 it! I don't know the implications of having your customWin become an attribute of the parent window. Neither for giving it a slot after 'show ', neither of deleting an attribute. The example I had given was much simpler, I had no exceptions, errors or crashes at all I'm going to try and make it look like yours, but other factors in the complexity of your program may be causing this.
I still have troubles not having a slot call twice for a table cell double click, so tiny problems creep up in PyQt sometimes BUT: - what is this destroyed Signal you're using?
Is it you that emits it at the secondary window close? I'll try to explain what I'm doing. I have a main windows with comboboxes filled in from an xml file 2. The main window does some calculations based on selected combobox values the main window works perfectly 3. I could do the same with a QDialog but then I need to add much more inputs to emulate the bars functionality 4.
But when the other window is closed, all combobox values are updated from the just refreshed xml file. This all works perfectly well if the new data editing window is opened and closed once.
This is because I instantiate a new window, show it and then close it. All fine once. But when I open another window again if one wanted to edit the data again , it opens fine but on closing that window the whole application simply crashes without error. I think the problem is because I close the other window with self. And I update the main window on the second window closed signal. Then when I open another window new object and close that there's a conflict between the first window object and the second which both try to emit the closed signal and update the main window, so it crashes.
This is my take on this. Read of address C. So my initial question was how to destroy a window in Python? If I can properly destroy the second window and update the main one on either its destroyed or closed signal, I think it should work.
Is there not way to hide instead of close the window in QT? Then you could create window hidden and then only show it when needed and afterwards hide it again. If that window have different menus and even tool bar, I would call it different application and implement it separately, then use passing of data between programs. You can use brew to install pyqt in the terminal :. Python is often installed by default on Linux in nearly all of the distributions including Ubuntu. But you want to make sure to use Python 3, because of all the features and ease of use.
You can verify that you have the newest Python version with the command:. On Ubuntu Linux they sometimes include two versions of python, python3 and python. First we'll create a series of simple windows on your desktop to ensure that PyQt is working and introduce some of the basic concepts.
Then we'll take a brief look at the event loop and how it relates to GUI programming in Python. Finally we'll look at Qt's QMainWindow which offers some useful common interface elements such as toolbars and menus. These will be explored in more detail in the subsequent tutorials.
Let's create our first application! To start create a new Python file — you can call it whatever you like e. We'll write our simple app in this file. We'll be editing within this file as we go along, and you may want to come back to earlier versions of your code, so remember to keep regular backups. The source code for the application is shown below.
Type it in verbatim, and be careful not to make mistakes. If you do mess up, Python will let you know what's wrong. First, launch your application.
You can run it from the command line like any other Python script, for example Run it! You will now see your window. Qt automatically creates a window with the normal window decorations and you can drag it around and resize it like any window. What you'll see will depend on what platform you're running this example on.
Our window, as seen on Windows, macOS and Linux. First, we import the PyQt classes that we need for the application. Next we create an instance of QApplication , passing in sys. If you know you won't be using command line arguments to control Qt you can pass in an empty list instead, e. Next we create an instance of a QWidget using the variable name window.
In Qt all top level widgets are windows -- that is, they don't have a parent and are not nested within another widget or layout. This means you can technically create a window using any widget you like.
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