We Keep Coding

PyQt QRadioButton toggled singal callback execute after delete [duplicate]

There are some examples of removing specific items from a layout, but I can not find anything on simply deleting everything from a frame.
Using pyqt designer, I have created a frame. Then using pyuic4 the file is converted to python. In the main program, some layouts, items, and widgets are dynamically inserted to the frame. However, I dont actually keep track of all the items. On a button refresh, I want to delete everything contained in the frame and populate it again.
My question is, is there a simple way to delete everything that is contained in a frame, including layouts, widgets, and items.
As of now, I can do:
for i in range(len(MyResourceFrame.children())):
MyResourceFrame.children()[i].deleteLater()
However, I have code directly under that, and after the first qframe population, clicking on repopulate give the error that a frame is already there, which then removes all items. The second click on repopulate works. Does this have something to do with "Later" wanting to be out of scope first or is that just a name?

The deleteLater slot will just schedule the object for deletion. That is, the object won't be deleted until control returns to the event loop (which will usually mean after the currently executing function has returned).
If you want to delete an object immediately, use the sip module. This should allow you delete a layout and all its contained widgets like this:
PyQt5:
from PyQt5 import sip
...
class Window(QtWidgets.QMainWindow):
...
def populateFrame(self):
self.deleteLayout(self.frame.layout())
layout = QtWidgets.QVBoxLayout(self.frame)
...
def deleteLayout(self, layout):
if layout is not None:
while layout.count():
item = layout.takeAt(0)
widget = item.widget()
if widget is not None:
widget.deleteLater()
else:
self.deleteLayout(item.layout())
sip.delete(layout)
PyQt4:
import sip
...
class Window(QtGui.QMainWindow):
...
def populateFrame(self):
self.deleteLayout(self.frame.layout())
layout = QtGui.QVBoxLayout(self.frame)
...
def deleteLayout(self, layout):
if layout is not None:
while layout.count():
item = layout.takeAt(0)
widget = item.widget()
if widget is not None:
widget.deleteLater()
else:
self.deleteLayout(item.layout())
sip.delete(layout)

The problem was the layout predefined inside your QFrame. If you remove it in QtDesigner your frame will appear correctly with the first click.

QScrollArea, how do I make my central widget scrollable? [duplicate]

This question already has an answer here:
How to use QScrollArea to make scrollbars appear
(1 answer)
Closed 2 years ago.
I'm trying to turn a widget into a scrollable window. However, all I've accomplished is opening a QScrollarea that's completely independent from my central widget.
class Ui_MainWindow(object):
def mainscreen(self, MainWindow):
self.centralwidget = QtWidgets.QWidget(MainWindow)
self.scrollArea = QtWidgets.QScrollArea()
self.scrollArea.setWidget(self.centralwidget)
MainWindow.setCentralWidget(self.centralwidget)
if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
MainWindow = QtWidgets.QMainWindow()
ui = Ui_MainWindow()
ui.mainscreen(MainWindow)
MainWindow.show()
app.exec_()
This just opens up my MainWindow on its own, only way I get an scrollarea open is if I do self.scrollarea.show . I cant figure out how QScrollArea works, how am I supposed to do it?

Simple explanation: the scroll area has no relation with the main window, and then it's not shown when the main window is.
Never, ever modify (or imitate) files generated by pyuic
You are making some confusion around the object structure, Qt parent/ownership and how a scroll area is set up.
This is also caused by the fact that you're clearly trying to mimic the structure and behavior of a file generated by pyuic, which should never be done. Those files are intended to be directly used as they are, without any modification, and imported in the main script of your program.
Their peculiar structure is intended only for that purpose, and the way they're built is not to be emulated, as creation of UI by code should only be done by subclassing a QWidget subclass (QMainWindow, QDialog, etc); trying to imitate what they do is not only unnecessary, but most times leads to confusion, bugs and unexpected behavior, exactly like in your case.
The only valid reason to open (and just read) a file generated by pyuic is to learn how widgets are created in the setupUi, keeping in mind that the setupUi argument (usually, MainWindow for QMainWindows, Form for QWidgets, Dialog for QDialogs, unless the name of the top level widget is changed in the object inspector of designer) is the main widget on which the ui is built upon.
Manually editing those files should only be done if one really knows what she/he is doing. There are few, very rare cases for which this is considered necessary, and it's usually to workaround very specific known bugs in the uic module, that normally rise on very specific conditions and situations.
What is happening?
Then, when a QWidget instance is created with an existing widget as argument, the result is that the new widget becomes a child of the existing one.
Widget can be then reparented in various ways: by setting a widget for a scroll area using setWidget(), or by setting the widget as a central widget to a QMainWindow.
What happens with your code is that you created a new QWidget that becomes a child of the QMainWindow with the following line:
self.centralwidget = QtWidgets.QWidget(MainWindow)
Then you create a scroll area (without any parent):
self.scrollArea = QtWidgets.QScrollArea()
Widgets that are not created with a parent are normally considered top level windows, unless they are added to a layout (or manually reparented using setParent(), but that's another story), which causes the parent (the widget on which the layout is set) to take ownership of the new child widget. Otherwise, if you try to show the "parent-less" widget, it will be shown as a top level widget, meaning it will have its own window, and as any top level widget, they can only be shown by manually calling show() or setVisible(True) (and that's your case).
Then you try to set the centralwidget of the scroll area, which will result in reparenting it:
self.scrollArea.setWidget(self.centralwidget)
Finally, you're setting that widget as the central widget, which will reparent it back again to the main window, with the result that the scroll area will not have a widget anymore (QObjects, from which QWidget inherits, can only have a single parent).
MainWindow.setCentralWidget(self.centralwidget)
The correct approach
The solution is to correctly create a QWidget (or QMainWindow in your case) subclass, set the scroll area as the central widget (if you want it as that) and create a new widget for its contents:
class MainWindow(QtWidgets.QMainWindow):
def __init__(self):
super().__init__()
self.scrollArea = QtWidgets.QScrollArea()
self.setCentralWidget(self.scrollArea)
self.scrollArea.setWidgetResizable(True)
self.contents = QtWidgets.QWidget()
self.scrollArea.setWidget(self.contents)
# create a layout for the scroll area contents; using the target widget
# as argument of the layout constructor automatically sets the layout on
# the specified widget
layout = QtWidgets.QVBoxLayout(self.contents)
# the same as:
# layout = QtWidgets.QVBoxLayout()
# self.contents.setLayout(layout)
for row in range(20):
button = QtWidgets.QPushButton('button {}'.format(row + 1))
layout.addWidget(button)
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
mainWindow = MainWindow()
mainWindow.show()
sys.exit(app.exec_())

In PyQT why somes widgets needs the "self" parameter before calling them, while others don't

I'm a little bit confused about the use of the "self" parameter with some widgets like (QLineEdit), indeed when learning to use the QLabel widget, I used to call the class without the self paramater, or when using the QLineEdit widget, the widget wouldn't work without the "self" parameter, here's the code I'm working on :
# Import necessary modules
import sys
from PyQt5.QtWidgets import QApplication, QWidget, QLabel, QLineEdit, QPushButton
from PyQt5.QtCore import Qt
class EntryWindow(QWidget): # Inherits QWidget
def __init__(self): # Constructor
super().__init__() # Initializer which calls constructor for QWidget
self.initializeUI() # Call function used to set up window
def initializeUI(self):
"""
Initialize the window and display its contents to the screen
"""
self.setGeometry(400, 300, 400, 200)
self.setWindowTitle('QLineEdit Widget')
self.displayWidgets()
self.show() # Show everything
def displayWidgets(self):
'''
Setup the QLineEdit and other widgets.
'''
# Create name label and line edit widgets
QLabel("Please enter your name below.", self).move(100, 20)
name_label = QLabel("Name:", self)
name_label.move(55, 70)
self.name_entry = QLineEdit(self)
self.name_entry.move(120, 68)
self.name_entry.resize(200, 25) # Change size of entry field
self.name_entry.setAlignment(Qt.AlignLeft) # The default alignment
text_font = self.name_entry.font() # Get font option from the Qlineedit
text_font.setPointSize(12) # Modify font size
#text_font.setBold(True) # Bold
self.name_entry.setFont(text_font) # Apply font
self.clear_button = QPushButton('Clear text', self)
self.clear_button.clicked.connect(self.clearEntries)
self.clear_button.move(120, 130)
self.exit_button = QPushButton("Exit", self)
self.exit_button.clicked.connect(self.exitApplication)
self.exit_button.move(240, 130)
def clearEntries(self):
sender = self.sender()
if sender.text() == 'Clear text':
self.name_entry.clear()
def exitApplication(self):
sender = self.sender()
if sender.text() == "Exit":
self.close() # Close the window
# Run program
if __name__ == '__main__':
app = QApplication(sys.argv)
window = EntryWindow()
sys.exit(app.exec_())
So here is where I'm confused, when using QLabel, I didn't have to put the "self" parameter before, or when using QLineEdit, I had to put "self" otherwise my code wouldn't work :
QLabel("Please enter your name below.", self).move(100, 20)
self.name_entry = QLineEdit(self)

First of all, the problem or difference has nothing to do with the "self", but what it is for, pre-established rules in Qt design.
In Qt there is a hierarchy tree between the QObjects where it is established that the parent QObject manages the memory (the life cycle of its children) so if the parent deleted the children, they will also be deleted. This allows avoiding memory leaks since many QObjects are generally used in many applications.
On the other hand, that concept of kinship is also passed to QWidgets since they are also QObjects, but there is also another characteristic: a QWidget in general will be drawn on top of its parent. So if you want the QLineEdit and QLabel to be part of the window then they must be children of the window so it is necessary that you pass the window object which is "self" as parent.
So when you go to the window (in this case "self") you avoid 2 problems:
That the object has a longer life cycle (the same as the window).
And you make the widget (either QLabel or QLineEdit) be placed on top of the window.

The self name is a Python convention to indicate the instance of an object. When set as argument in an object constructor, it's normally used to give the new object a reference to the one that created it, and that's normally called a "parent". Note that while self is usually used as parent argument, you can set any QWidget instance as parent.
In Qt terms, not only it indicates the roles in a "parentship" of the object structure, but also results in two important aspects:
In the world of QObjects (from which QWidget inherits) this helps for memory management: when a parent is deleted, all its children objects are deleted as well. It's also useful to find child objects (using findChild() or findChildren()) which are direct children or [great, ...] grandchildren of another.
When creating a widget with a QWidget parent, that widget is also only "drawn inside" it: it can only be visible within the boundaries of the parent, not outside it; note that this is usually optional, as most times you'll add a widget to a layout manager (but you didn't), which automatically reparents the widget to the widget that is managed by that layout: if it was a child of another widget, it's removed from that and added to the new one. Also consider that if a widget has no parent and is not added to a layout, it's considered a "top level widget" (a standalone window), and if show() or setVisible(True) is called it will have its own window.
This means that if the widget has a parent and the parent becomes visible, the child will be automatically visible too (unless hide() or setVisible() was explicitly called).
Note that while a QWidget that has no parent is always a top level window, a widger that has a parent could be a top level window, and that happens if it has the QtCore.Qt.Window flag set (using the f keyword in the constructor, or with setWindowFlags()). This is useful when the widget has to be a top level window, but the parentship must still be preserved, not only for memory management (when the parent window is closed and deleted, any child should be deleted as well) but for interaction purposes: for example, with QDialogs (which are standalone windows) it's important to set the parent, so that they can be modal to that parent, meaning that no keyboard/mouse interaction can happen on the parent until the dialog is closed.
Finally, it's important to remember that creating widgets "on the fly" in python has a (sometimes perceived incoherent) result: if no python reference is given to the widget but the widget has a parent, it won't garbage collected.
Consider the following:
def test1(self):
someDialog = QtWidgets.QDialog()
someDialog.show()
This will probably show a window just for an instant, and then it will disappear instantly.
def test2(self):
someDialog = QtWidgets.QDialog(self)
someDialog.show()
In this case, the dialog will not disappear, that's because it has a parent, PyQt knows it, and it will not try to delete it.
Even this is actually valid (but, no, don't do it):
def test2b(self):
QtWidgets.QDialog(self).show()
Similar result, but only apparently:
def test3(self):
self.someDialog = QtWidgets.QDialog()
self.someDialog.show()
In the case above, the visual result will be probably the same as test2, but if test3 is called again while the dialog is still visible, it will delete the current one and create a new one: that's because the dialog has no parent, and overwriting self.someDialog with a new instance will cause python to release the previous one, which will tell Qt that it can safely erase it, since it has no parent.
Finally, it's not necessary to set the parent to widgets, as long as they are added to a layout (which is the preferred approach, as using fixed geometries is highly discouraged), since the layout will automatically set the parent anyway as soon as it's [going to be] set on the actual parent.
Note that QDialog is normally shown with exec_() in order to correctly display it as modal of the parent and use it as it should.

Note the import statements at the top
from PyQt5.QtWidgets import QApplication, QWidget, QLabel, QLineEdit, QPushButton
QLabel and QLineEdit as can be seen in the documentations
https://doc.qt.io/qtforpython/PySide2/QtWidgets/QLabel.html
https://doc.qt.io/qtforpython/PySide2/QtWidgets/QLineEdit.html
both take a QWidget as a parameter. The self passed as the second parameter indicates the current QWidget type. For other methods inside the class, self is used to invoke the instance methods.

Move pyqt button out of list of buttons

I have a list of pyqt4 push button and want to move the position. Since it is troublesome it make lots of buttons variable I create them through a list. The code below
import sys
from PyQt5.QtWidgets import QApplication, QPushButton, QWidget, QVBoxLayout
class Window(QWidget):
def __init__(self):
QWidget.__init__(self)
layout = QVBoxLayout(self)
self.buttons = []
for i in range(3):
self.buttons.append(QPushButton('',self))
self.buttons[-1].setFixedWidth(50)
self.buttons[-1].setFixedHeight(50)
self.buttons[-1].move(70*i+50,300)
layout.addWidget(self.buttons[-1])
if __name__ == '__main__':
import sys
app = QApplication(sys.argv)
window = Window()
window.resize(500,500)
window.show()
sys.exit(app.exec_())
don't work for specify the position
but
class Window(QWidget):
def __init__(self):
QWidget.__init__(self)
layout = QVBoxLayout(self)
self.button1 = QPushButton('',self)
self.button1.setFixedWidth(50)
self.button1.setFixedHeight(50)
self.button1.move(50,300)
self.button2 = QPushButton('',self)
self.button2.setFixedWidth(50)
self.button2.setFixedHeight(50)
self.button2.move(120,300)
self.button3 = QPushButton('',self)
self.button3.setFixedWidth(50)
self.button3.setFixedHeight(50)
self.button3.move(190,300)
layout = QVBoxLayout(self)
layout.addWidget(self.button1)
layout.addWidget(self.button2)
layout.addWidget(self.button3)
works fine.
What's the reason behind?

If you want to manually specify the geometry (position and size) of widgets, you should not add them to a layout.
Your second example "works" just because you already created and set a layout to the top-level widget (the Window class), and since a layout already exists the second one is not "installed". Running it from the console will shows this error:
StdErr: QLayout: Attempting to add QLayout "" to Window "", which already has a layout
When a widget is added to a layout, the ownership of the "layout item" (an abstract item used by layouts to manage its widgets) is transferred to the layout, and the widget is reparented to the widget that uses that layout.
Since the second layout cannot be set, it will not manage the geometries of the items you tried to add, and the result is that they will keep the geometries you set before.
The same result can be obtained if you remove all the last lines referencing the other layout, which is exactly what you need.
Also, note that in order to add a widget that is not managed by a layout, a parent is required. Your last example also works because you specified the window as the parent while instantiating them; if you don't do that the buttons will not be shown, but if you do show them (with show() or setVisible(True)) they will each appear in separate windows, as they will become their own top level windows.
If you don't have other widgets that should be managed by a layout, you can also avoid creating the first layout at all (but, still, the parent is required).
Finally, let me tell you that using manual geometries is generally discouraged, and there are very few and specific cases for which it's a good idea to go with.
The main reason behind this is that widgets tend to show very differently from device to device, and that depends on various aspects:
different OS and OS versions draw widgets differently (sometimes dramatically), and this involves varying the widget size and behavior; while this might not be a major issue for simple widgets, it can be a problem for things like item views, spinboxes, etc;
different OS and systems use different styles, which also includes things like internal widget content margins and minimum size;
specific system settings (most importantly, the default font) could make widgets mostly unreadable, specifically with text being clipped within the widget margins if the font size is too big;
depending on the OS, you might face issues if the system uses High DPI displays, and you could end up with very tiny widgets that are almost impossible to interact with;
fixed geometries force you (and the user) to have a fixed widget/window size, and (along with the DPI issue above) this can be a problem: the same widget could look too big or too small;

Trying to make a collapsible widget: How to hide/unhide all child widgets?

Im making a simplish widget that can act as a container for other widgets. One of the features of the widget is that you can expand/collapse it by clicking on it. My current method is basically looking up all child widgets of the layout and hiding them. I'm looking for any help on how to handle this properly - my current implementation has at least one serious caveat: that you can't add widgets while it's collapsed (they're added in an 'unhidden' state)
heres the setCollapsed method that is run when the widget is clicked
def collapsed(self):
return self._isCollapsed
def setCollapsed(self, collapseBool):
self._isCollapsed = collapseBool
if self.layout()!=None:
childWidgets = [self.layout().itemAt(i).widget() for i in range(self.layout().count())]
for w in childWidgets:
if isinstance(w,QtGui.QWidget):
w.setHidden(collapseBool)
if collapseBool:
self._cachedMargin = self.layout().margin()
self.layout().setMargin(0)
else:
self.layout().setMargin(self._cachedMargin)

Rather than hiding all child widgets individually, I would just hide a single parent item.