I am beginning to write a GUI using PyQt4. This is my first experience with GUIs (and also oo-programming is somewhat new to me). Part of that GUI will be like 4 to 5 instances of QComboBox. As many choices are to be made, I want the user to be able to lock a choice, such that is not being changed unintenionally later. For one QComboBox I can solve the problem with this code that I wrote:
import sys
from PyQt4 import QtGui, QtCore
class MyGui(QtGui.QWidget):
def __init__(self):
QtGui.QMainWindow.__init__(self)
self.resize(250, 50)
# vertical layout for widgets
self.vbox = QtGui.QVBoxLayout()
self.setLayout(self.vbox)
# Create a combo box with some choices
self.combo_color = QtGui.QComboBox()
self.vbox.addWidget(self.combo_color)
items = 'Red Yellow Purple'.split()
self.combo_color.addItems(items)
self.connect(self.combo_color, QtCore.SIGNAL('activated(QString)'), self.use_choice)
# add a checkbox next to the combobox which (un-)locks the the combo-choice
self.checkbox_color = QtGui.QCheckBox('Lock Choice', self)
self.vbox.addWidget(self.checkbox_color)
self.connect(self.checkbox_color, QtCore.SIGNAL('stateChanged(int)'), self.lock_choice)
def use_choice(self, text):
# do something very useful with the choice
print 'The current choice is: {choice}'.format(choice=text)
def lock_choice(self):
if self.checkbox_color.isChecked():
self.combo_color.setEnabled(False)
print 'Choice {choice} locked'.format(choice=self.combo_color.currentText())
else:
self.combo_color.setEnabled(True)
print 'Choice unlocked'
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
mygui = MyGui()
mygui.show()
app.exec_()
This code does what it should, but I am very unhappy with its design, because the method lock_choice is hard-coded to only lock the choice of the QComboBox combo_color. What if I now want to do the same thing for another QComboBox (say combo_name) and a second QCheckBox (say checkbox_name) which could be realized by appending the following code to the classes __init__(self) code block:
# create second combo box with some other choices
self.combo_name = QtGui.QComboBox()
self.vbox.addWidget(self.combo_name)
items = 'Bob Peter'.split()
self.combo_name.addItems(items)
self.connect(self.combo_name, QtCore.SIGNAL('activated(QString)'), self.use_choice)
# add a checkbox next to the combobox which (un-)locks the the combo-choice
self.checkbox_name = QtGui.QCheckBox('Lock Choice', self)
self.vbox.addWidget(self.checkbox_name)
self.connect(self.checkbox_name, QtCore.SIGNAL('stateChanged(int)'), self.lock_choice) # <-- obviously wrong, as it (un-)locks color choice at the moment
Both QComboBoxes can share the method use_choice() right now, but they cannot share the method lock_choice(), as both checkboxes lock the color-choice. I want the checkbox checkbox_name to lock the name-choice, without copy and pasting the current lock_choice()-method and switching the hardcoded combobox.
I am sure there is an easy way, like passing the target-combobox to the method, which i just don't know yet. Help would be appreciated!
Try partial functions-
from functools import partial
with the connect signal, pass the QWidget name:
self.connect(self.checkbox_color, QtCore.SIGNAL('stateChanged(int)'), partial(self.lock_choice, self.combo_color))
And in your method, you may add an argument.
We'll add an argument in the method like below, to handle the QWidget(QComboBox) that we'll pass through the partial function above.
def lock_choice(self, combos):
if combos.isEnabled(True):
combos.setEnabled(False)
print 'Choice {choice} locked'.format(choice=combos.currentText())
The simplest solution would be to use the toggled signal with the setDisabled slot:
self.checkbox_color.toggled.connect(self.combo_color.setDisabled)
(And note how much cleaner the new-style sytax is when making signal connections).
It's also worth pointing out that you can also use a lambda for making inline signal connections, like this:
self.checkbox_color.toggled.connect(
lambda checked: self.combo_color.setDisabled(checked))
This is probably the most idiomatic solution when there are no convenient signal/slot pairings (and of course partial functions can achieve more or less the same thing in different way).
Related
I have been trying to get a QComboBox in PyQt5 to become populated from a database table. The problem is trying to find a method that recognizes a click event on it.
In my GUI, my combo-box is initially empty, but upon clicking on it I wish for the click event to activate my method for communicating to the database and populating the drop-down list. It seems so far that there is no built-in event handler for a click-event for the combo-box. I am hoping that I am wrong on this. I hope someone will be able to tell me that there is a way to do this.
The best article I could find on my use-case here is from this link referring to PyQt4 QComboBox:
dropdown event/callback in combo-box in pyqt4
I also found another link that contains a nice image of a QComboBox.
The first element seems to be a label followed by a list:
Catch mouse button pressed signal from QComboBox popup menu
You can override the showPopup method to achieve this, which will work no matter how the drop-down list is opened (i.e. via the mouse, keyboard, or shortcuts):
from PyQt5 import QtCore, QtWidgets
class ComboBox(QtWidgets.QComboBox):
popupAboutToBeShown = QtCore.pyqtSignal()
def showPopup(self):
self.popupAboutToBeShown.emit()
super(ComboBox, self).showPopup()
class Window(QtWidgets.QWidget):
def __init__(self):
super(Window, self).__init__()
self.combo = ComboBox(self)
self.combo.popupAboutToBeShown.connect(self.populateConbo)
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(self.combo)
def populateConbo(self):
if not self.combo.count():
self.combo.addItems('One Two Three Four'.split())
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec_())
However, for your particular use-case, I think a better solution might be to set a QSqlQueryModel on the combo-box, so that the items are updated from the database automatically.
Alternative Solution I :
We can use frame click, the code is to be used in the container of the combo box (windows/dialog/etc.)
def mousePressEvent(self, event):
print("Hello world !")
or
def mousePressEvent():
print("Hello world !")
Alternative Solution II :
We could connect a handler to the pressed signal of the combo's view
self.uiComboBox.view().pressed.connect(self.handleItemPressed)
...
def handleItemPressed(self, index):
item = self.uiComboBox.model().itemFromIndex(index)
print("Do something with the selected item")
Why would you want to populate it when it's activated rather than when the window is loaded?
I am currently developing an application with PySide (another Python binding for the Qt framework), and I populate my comboboxes in the mainwindow class __init__ function, which seems to be the way to go, judging by many examples.
Look at the example code under "QCombobox" over at Zetcode.
I'm not sure what to call it. I want to know how to make one of those menus where you use the arrow keys to highlight your options and press enter to accept it.
The questioner acknowledged being unsure how to clearly state what they're after (I know the feeling!) and it is a little while after the question was posted, but in light of their comment suggesting they were after text, I believe something like python-prompt-toolkit, which is used to provide text-based autocomplete in a number of Python projects, may offer a solution.
There is documentation here which has this example of using a WordCompleter:
from prompt_toolkit import prompt
from prompt_toolkit.completion import WordCompleter
html_completer = WordCompleter(['<html>', '<body>', '<head>', '<title>'])
text = prompt('Enter HTML: ', completer=html_completer)
print('You said: %s' % text)
That produces output like this:
The example above is still relatively like a ComboBox merely rendered in text, but there are ways to produce other styles of menu as shown in the gallery here.
If that isn't sufficient then another option is looking into something that wraps ncurses, like https://bitbucket.org/npcole/npyscreen or http://urwid.org/ .
The answer to your question including the examples you provided is curses. This package is very much dependent on the underlying operating system. So if platform independence is key then you will get issues. There is for example a Windows port UniCurses but your implementation has to handle this switch if necessary.
There are also tools built on top of curses. Four example Urwid.
I personally have some experience with curses and if you have Linux as the underlying system this can be fun if your requirements are robust and simple. Like your menu requirement. I have to say though that the learning curve is pretty steep.
Hope this helps. But given the broad question thus is the only level of detail to provide at this stage.
I think you mean Combobox.
Here is a short example based on this and PyQt:
from PyQt4 import QtGui, QtCore
import sys
class CheckableComboBox(QtGui.QComboBox):
def __init__(self):
super(CheckableComboBox, self).__init__()
self.view().pressed.connect(self.handleItemPressed)
self.setModel(QtGui.QStandardItemModel(self))
def handleItemPressed(self, index):
item = self.model().itemFromIndex(index)
if item.checkState() == QtCore.Qt.Checked:
item.setCheckState(QtCore.Qt.Unchecked)
else:
item.setCheckState(QtCore.Qt.Checked)
class Dialog_01(QtGui.QMainWindow):
def __init__(self):
super(QtGui.QMainWindow,self).__init__()
myQWidget = QtGui.QWidget()
myBoxLayout = QtGui.QVBoxLayout()
myQWidget.setLayout(myBoxLayout)
self.setCentralWidget(myQWidget)
self.toolbutton = QtGui.QToolButton(self)
self.toolbutton.setText('Select Categories ')
self.toolmenu = QtGui.QMenu(self)
for i in range(3):
action = self.toolmenu.addAction("Category " + str(i))
action.setCheckable(True)
self.toolbutton.setMenu(self.toolmenu)
self.toolbutton.setPopupMode(QtGui.QToolButton.InstantPopup)
myBoxLayout.addWidget(self.toolbutton)
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
combo = Dialog_01()
combo.show()
combo.resize(480,320)
sys.exit(app.exec_())
So I am generating a menu of options based on some files on my system. I have a list list of objects I need to dynamically generate an option in the menu for and need to be able to let the function that is doing the creation know which object to use. After some research I found the post below. I could not comment as my rep is not high yet: How to pass arguments to callback functions in PyQt
When I run this the signal mapper is not working right. It is not even calling the handleButton correctly. Any ideas as to how to use the signal mapper correctly?
from PyQt4 import QtGui, QtCore
class Window(QtGui.QMainWindow):
def __init__(self):
QtGui.QMainWindow.__init__(self)
self.mapper = QtCore.QSignalMapper(self)
self.toolbar = self.addToolBar('Foo')
self.toolbar.setToolButtonStyle(QtCore.Qt.ToolButtonTextOnly)
for text in 'One Two Three'.split():
action = QtGui.QAction(text, self)
self.mapper.setMapping(action, text)
action.triggered.connect(self.mapper.map)
self.toolbar.addAction(action)
self.mapper.mapped['QString'].connect(self.handleButton)
self.edit = QtGui.QLineEdit(self)
self.setCentralWidget(self.edit)
def handleButton(self, identifier):
print 'run'
if identifier == 'One':
text = 'Do This'
print 'Do One'
elif identifier == 'Two':
text = 'Do That'
print 'Do Two'
elif identifier == 'Three':
print 'Do Three'
text = 'Do Other'
self.edit.setText(text)
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Window()
window.resize(300, 60)
window.show()
sys.exit(app.exec_())
EDIT:
I've found that by using old-style signal/slot connections this is fixed:
#action.triggered.connect(self.mapper.map)
self.connect(action, QtCore.SIGNAL("triggered()"), self.mapper, QtCore.SLOT("map()"))
and
#self.mapper.mapped['QString'].connect(self.handleButton)
self.connect(self.mapper, QtCore.SIGNAL("mapped(const QString &)"), self.handleButton)
Am I using the new-style connections incorrectly?
Based on this post as well as the original link I posted, I thought I was doing things correctly.
The original example code (which I wrote), works perfectly fine for me using either Python2 or Python3 with several different recent versions of PyQt4. However, if I use a really old version of PyQt4 (4.7), the handler no longer gets called.
The reason (and solution) for this is given in the response to the mailing list post you linked to:
It's actually a problem with QSignalMapper.map() being called from a
proxy rather than new-style connections.
The workaround is to explicitly specify a signal that is compatible
with map()...
self.b1.clicked[()].connect(self.mapper.map)
Tonight's PyQt snapshot will be smarter about finding a usable Qt slot
before deciding that it needs to use a proxy so that the workaround
won't be necessary.
There are some signals (like clicked and triggered) which always send a default value unless you explicitly request otherwise. With the old-style signals, you can specify the no default overload it with SIGNAL("triggered()"), but with new-style signals, you have to do it like this:
action.triggered[()].connect(self.mapper.map)
But that is only necessary with very old versions of PyQt4 - the underlying issue was fixed back in 2010 (don't know the exact version, but 4.8 should be okay).
I know this has been asked many times before. I read all of those threads, and my case seems different. Everybody else who has this trouble has a few straightforward causes that I think I’ve ruled out, such as:
Starting a timer with no event loop running
Starting/stopping a timer from a thread other than the one that created the timer
Failing to set the parent property of a widget, leading to problems with the order of destruction
Below I have a minimal code sample that demonstrates the problem. Notice that I’ve started no threads or timers. I also have set the parent of every widget. If I remove the graph widgets, the problem goes away, so one is tempted to blame pyQtGraph, however, if I include the plot widgets but exclude all the blank tabs (i.e. every tab except tabCatchaTiger), the problem also goes away, and that seems to vindicate pyQtGraph.
Versions:
Windows 7
Python 2.7.8
Wing IDE 5.0.9-1
PyQt 4.11.1
PyQwt 5.2.1
PyQtGraph 0.9.8
Test case:
from PyQt4 import Qt, QtGui, QtCore
import PyQt4.Qwt5 as Qwt
import pyqtgraph as pg
pg.functions.USE_WEAVE = False # Lets pyqtgraph plot without gcc
pg.setConfigOption('background', 'w')
pg.setConfigOption('foreground', 'k')
# GUI for visualizing data from database
class crashyGUI(QtGui.QWidget) :
def __init__(self) :
# Make the window
QtGui.QWidget.__init__(self)
self.resize(700, QtGui.QDesktopWidget().screenGeometry(self).height()*.85)
self.setWindowTitle('Data Visualization')
# Create tab interface
tabWidget = QtGui.QTabWidget(self)
# define the tab objects
self.tabEeny = QtGui.QWidget(tabWidget)
self.tabMeeny = QtGui.QWidget(tabWidget)
self.tabMiney = QtGui.QWidget(tabWidget)
self.tabMoe = QtGui.QWidget(tabWidget)
self.tabCatchaTiger = QtGui.QWidget(tabWidget)
self.tabByThe = QtGui.QWidget(tabWidget)
self.tabToe = QtGui.QWidget(tabWidget)
# Initialize the tab objects
self.initTabCatchaTiger()
###########################################
############### Main Layout ###############
###########################################
tabWidget.addTab(self.tabEeny, 'Eeny')
tabWidget.addTab(self.tabMeeny, 'Meeny')
tabWidget.addTab(self.tabMiney, 'Miney')
tabWidget.addTab(self.tabMoe, 'Moe')
tabWidget.addTab(self.tabCatchaTiger, 'Catch a Tiger')
tabWidget.addTab(self.tabByThe, 'By The')
tabWidget.addTab(self.tabToe, 'Toe')
self.mainLayout = QtGui.QVBoxLayout(self)
self.mainLayout.addWidget(tabWidget)
self.setLayout(self.mainLayout)
def initTabCatchaTiger(self):
###########################################
############# ADC Capture Tab #############
###########################################
# define tab layout
grid = QtGui.QGridLayout(self.tabCatchaTiger)
# create copy of adc plot and add to row 3 of the grid
self.catchaTigerPlot1 = pg.PlotWidget(name = 'Catch a Tiger 1', parent = self.tabCatchaTiger)
self.catchaTigerPlot1.setTitle('Catch a Tiger 1')
grid.addWidget(self.catchaTigerPlot1, 2, 0, 1, 8)
self.catchaTigerPlot2 = pg.PlotWidget(name = 'Catch a Tiger 2', parent = self.tabCatchaTiger)
self.catchaTigerPlot2.setTitle('Catch a Tiger 2')
grid.addWidget(self.catchaTigerPlot2, 3, 0, 1, 8)
# set layout for tab
self.tabCatchaTiger.setLayout(grid)
def closeEvent(self, event) :
pass
def main() :
# open a QApplication and dialog() GUI
app = QtGui.QApplication([])
windowCrashy = crashyGUI()
windowCrashy.show()
app.exec_()
main()
There seem to be two closely-related issues in the example.
The first one causes Qt to print the QObject::startTimer: QTimer can only be used with threads started with QThread messages on exit.
The second one (which may not affect all users) causes Qt to print QPixmap: Must construct a QApplication before a QPaintDevice, and then dump core on exit.
Both of these issues are caused by python deleting objects in an unpredicable order when it exits.
In the example, the second issue can be fixed by adding the following line to the __init__ of the top-level window:
self.setAttribute(QtCore.Qt.WA_DeleteOnClose)
Unless QApplication.setQuitOnLastWindowClosed has been changed to False, this will ensure that the application quits at the right time, and that Qt has a chance to automatically delete all the children of the top-level window before the python garbage-collector gets to work.
However, for this to be completely successful, all the relevant objects must be linked together in a parent-child hierarchy. The example code does this where it can, but there seem to be some critical places in the initialization of the PlotWidget class where it is not done.
In particular, there is nothing to ensure that the central item of the PlotWidget has a parent set when it is created. If the relevant part of the code is changed to this:
class PlotWidget(GraphicsView):
...
def __init__(self, parent=None, background='default', **kargs):
GraphicsView.__init__(self, parent, background=background)
...
self.plotItem = PlotItem(**kargs)
# make sure the item gets a parent
self.plotItem.setParent(self)
self.setCentralItem(self.plotItem)
then the first issue with the QTimer messages also goes away.
Here's a better answer:
You are allowing the QApplication to be collected before python exits. This causes two different issues:
The QTimer error messages are caused by pyqtgraph trying to track its ViewBoxes after the QApplication has been destroyed.
The crash appears to be intrinsic to Qt / PyQt. The following crashes in the same way:
from PyQt4 import Qt, QtGui, QtCore
def main() :
app = QtGui.QApplication([])
x = QtGui.QGraphicsView()
s = QtGui.QGraphicsScene()
x.setScene(s)
x.show()
app.exec_()
main()
You can fix it by adding global app to your main function, or by creating the QApplication at the module level.
Try to write this in block of __init__:
self.setAttribute(Qt.WA_DeleteOnClose)
Personally, I don't put any effort into chasing exit crashes anymore--just use pg.exit() and be done with it.
(but if you do happen to find a bug in pyqtgraph, don't hesitate to open an issue on github)
I had this happen as well and in my case it was caused by a call to deleteLater() on the aboutToQuit-Signal of the application, like so:
def closeEvent(self, *args, **kwargs):
self.deleteLater()
if __name__ == "__main__":
application = QtWidgets.QApplication(sys.argv)
window = testApplication()
# Handle application exit
application.aboutToQuit.connect(window.closeEvent)
# System exit
sys.exit(application.exec_())
Getting rid of the deleteLater on the whole window seemed to solve it.
I can't find a way to hide QComboBox items. So far the only way to filter its items out is to delete the existing ones (with .clear() method). And then to rebuild the entire QComboBox again using its .addItem() method.
I would rather temporary hide the items. And when they are needed to unhide them back.
Is hide/unhide on QCombobox items could be accomplished?
In case someone still looking for an answer:
By default, QComboBox uses QListView to display the popup list and QListView has the setRowHidden() method:
qobject_cast<QListView *>(comboBox->view())->setRowHidden(0, true);
Edit: fix code according to #Tobias Leupold's comment.
Edit: Python version:
# hide row
view = comboBox.view()
view.setRowHidden(row, True)
# disable item
model = comboBox.model()
item = model.item(row)
item.setFlags(item.flags() & ~Qt.ItemIsEnabled)
# enable item
view.setRowHidden(row, false)
item.setFlags(item.flags() | Qt.ItemIsEnabled)
To build on what #kef answered:
(excuse the C++ on the python question)
By default the QComboBox will use a QListView for the view, thus you can do the following:
QListView* view = qobject_cast<QListView *>(combo->view());
Q_ASSERT(view != nullptr);
view->setRowHidden(row, true);
The one drawback with the above is, that even though the item will be hidden from the popup, the user can still select it using the mouse wheel. To overcome this add the following for the hidden row:
QStandardItemModel* model = qobject_cast<QStandardItemModel*>(combo->model());
Q_ASSERT(model != nullptr);
QStandardItem* item = model->item(row);
item->setFlags(item->flags() & ~Qt::ItemIsEnabled);
With the above the row will be hidden and the user will not be able to scroll to it with the mouse wheel.
To unhide it, just do the reverse:
view->setRowHidden(row, false);
item->setFlags(item->flags() | Qt::ItemIsEnabled);
You can use the removeItem() method to remove an item from the QComboBox.
void QComboBox::removeItem ( int index )
Removes the item at the given index from the combobox. This will update the current index if the index is removed.
This function does nothing if index is out of range.
If you don't know the index, use the findText() method.
There are no hide/unhide methods for QComboBox items.
Althought there is no direct way to hide the item of the QComboBox, but you can use QComboBox::setItemData and set the size to (0,0) to hide the item of QComboBox:
comboBox->setItemData(row, QSize(0,0), Qt::SizeHintRole);
Use the setVisible() to alter the visibility of your object:
.setVisible(False) # Not Visible
.setVisible(True) # Visible
To show the item again:
comboBox->setItemData(row, QVariant(), Qt::SizeHintRole);
Note: changing the SizeHintRole doesn't work on OS X.
I came across this thread after getting frustrated with a lack of hide functionality that would keep the item indexing etc.
I got it to work based on #Kef and #CJCombrink answers. This is basically just a python translation.
I had a problem with qobject_cast.
Solved it by setting .setView(QListView()) to the QComboBox.
combo=QComboBox()
combo.setView(QListView())
hide:
combo.view().setRowHidden(rowindex,True)
tmp_item=combo.model().item(rowindex)
tmp_item.setFlags(tmp_item.flags() & ~Qt.ItemIsEnabled)
unhide:
combo.view().setRowHidden(rowindex,False)
tmp_item=combo.model().item(rowindex)
tmp_item.setFlags(tmp_item.flags() | Qt.ItemIsEnabled)
I decided to subclass the QComboBox and add the hide functionality. Bellow is an use example for testing.
You are welcome to use it. I make no assurances.
import sys
from PySide2.QtWidgets import *
from PySide2.QtCore import *
from PySide2.QtGui import *
#subclassed QComboBox with added hide row functionality
class ComboBox_whide(QComboBox):
def __init__(self):
super().__init__()
self.setView(QListView())#default self.view() is a QAbstractItemView object which is missing setRowHidden, therefore a QListView needs to be set
def hide_row_set(self,row,value=True):
"""sets the row accesibility
value=True hides the row"""
self.view().setRowHidden(row,value)#hides the item from dropdown, however the item is stil accesible by moving down with arrow keys or mouse wheel. The following disables solves that
tmp_item=self.model().item(row)
if value:#hide -> disable
tmp_item.setFlags(tmp_item.flags() & ~Qt.ItemIsEnabled)
else:#enable
tmp_item.setFlags(tmp_item.flags() | Qt.ItemIsEnabled)
def hide_row_toggle(self,row):
"""toggles the row accesibility"""
if self.view().isRowHidden(row):#is hidden, therefore make available
self.hide_row_set(row,False)
else:#is not hidden, therefore hide
self.hide_row_set(row,True)
class Main(QMainWindow):
def __init__(self):
super().__init__()
cwidg=QWidget()
clayer=QVBoxLayout()
cwidg.setLayout(clayer)
self.setCentralWidget(cwidg)
#button for testing
self.btn=QPushButton('Button')
self.btn.setCheckable(True)
clayer.addWidget(self.btn)
#subclassed QComboBox
self.combo=ComboBox_whide()
for n in range(3):#add 3 items with tooltips
self.combo.addItem('item%i'%n)
self.combo.setItemData(n,'tip%i'%n,Qt.ToolTipRole)
clayer.addWidget(self.combo)
#button test function - choose either or for testing
self.btn.clicked.connect(self.btn_clicked)
#uncomment for add/remove example self.btn.clicked.connect(self.remove_add_item)
def btn_clicked(self):
self.combo.hide_row_toggle(1)
def remove_add_item(self):# here for naive comparison and to show why removing and adding is not ok
if self.combo.count()==3:
self.combo.removeItem(1)
else:
self.combo.addItem('new')#new "item1" withouth the ToolTip
if __name__ == '__main__':
app = QApplication.instance()
if app is None:#Pyside2 ipython notebook check
app = QApplication(sys.argv)
main = Main()
main.show()
app.exec_()