I have several QComboBoxes in my PyQt4/Python3 GUI and they are filled with some entries from a database during the initialisation. Initial CurrentIndex is set to 0. There is also a tick box which changes the language of the items in my combo boxes. To preserve current user selection I backup index of the current item and setCurrentIndex to this number after I fill in ComboBox with translated items. All those actions emit currentIndexChanged signal.
Based on the items selected in QComboBoxes some plot is displayed. The idea is to redraw the plot online - as soon as the user changes any of ComboBox current item. And here I have a problem since if I redraw the plot every time signal currentIndexChanged is emited, I redraw it also several times during initialization and if the translation tick box selection was changed.
What is the best way to separate these cases? In principle I need to separate programmical current Index Change from the user, and update the plot only in the later case (during GUI initialisation I can programically call update plot function once). Should I write/rewrite any signal? If so, I never did that before and would welcome any hint or a good example. Use another signal? Or maybe there is a way to temporary block all signals?
There are a few different things you can try.
Firstly, you can make sure you do all your initialization before you connect up the signals.
Secondly, you could use the activated signal, which is only sent whenever the user selects an item. (But note that, unlike currentIndexChanged, this signal is sent even if the index hasn't changed).
Thirdly, you could use blockSignals to temporarily stop any signals being sent while the current index is being changed programmatically.
Here's a script that demonstrates these possibilities:
from PyQt4 import QtGui, QtCore
class Window(QtGui.QWidget):
def __init__(self):
QtGui.QWidget.__init__(self)
layout = QtGui.QVBoxLayout(self)
self.combo = QtGui.QComboBox()
self.combo.setEditable(True)
self.combo.addItems('One Two Three Four Five'.split())
self.buttonOne = QtGui.QPushButton('Change (Default)', self)
self.buttonOne.clicked.connect(self.handleButtonOne)
self.buttonTwo = QtGui.QPushButton('Change (Blocked)', self)
self.buttonTwo.clicked.connect(self.handleButtonTwo)
layout.addWidget(self.combo)
layout.addWidget(self.buttonOne)
layout.addWidget(self.buttonTwo)
self.changeIndex()
self.combo.activated['QString'].connect(self.handleActivated)
self.combo.currentIndexChanged['QString'].connect(self.handleChanged)
self.changeIndex()
def handleButtonOne(self):
self.changeIndex()
def handleButtonTwo(self):
self.combo.blockSignals(True)
self.changeIndex()
self.combo.blockSignals(False)
def changeIndex(self):
index = self.combo.currentIndex()
if index < self.combo.count() - 1:
self.combo.setCurrentIndex(index + 1)
else:
self.combo.setCurrentIndex(0)
def handleActivated(self, text):
print('handleActivated: %s' % text)
def handleChanged(self, text):
print('handleChanged: %s' % text)
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec_())
Related
Need some help please to explain why the following does not work.
Environment: Python 3.4, Gtk3.0, limited experience of Python
File selectcontact.py contains code to select one of a number of records and pass its key back to its parent process for use in one of at least three other actions.
Code snippet from the parent class:
….
self.cindex = 0
….
def editcontact_clicked (self, menuitem):
import selectcontact
selectcontact.SelectContactGUI(self)
print ('From Manage ', self.cindex)
if self.cindex > 0:
import editcontact
editcontact.EditContactGUI(self.db, self.cindex)
….
Code snippet from selectcontact:
class SelectContactGUI:
def init(self, parent_class):
self.builder = Gtk.Builder()
self.builder.add_from_file(UI_FILE)
self.builder.connect_signals(self)
self.parent_class = parent_class
self.db = parent_class.db
self.cursor = self.db.cursor(cursor_factory = psycopg2.extras.NamedTupleCursor)
self.contact_store = self.builder.get_object('contact_store')
self.window = self.builder.get_object('window1')
self.window.show_all()
def select_contact_path(self, path):
self.builder.get_object('treeview_selection1').select_path(path)
def contact_treerow_changed (self, treeview):
selection = self.builder.get_object('treeview_selection1')
model, path = selection.get_selected()
if path != None:
self.parent_class.cindex = model[path][0]
print ('From select ', self.parent_class.cindex)
self.window.destroy()
….
window1 is declared as “modal”, so I was expecting the call to selectcontact to act as a subroutine, so that editcontact wouldn’t be called until control was passed back to the parent. The parent_class bit works because the contact_store is correctly populated. However the transfer back to the parent appears not to work, and the two print statements occur in the wrong order:
From Manage 0
From select 2
Comments gratefully received.
Graeme
"Modal" refers to windows only. That is, a modal window prevents accessing the parent window.
It has little to do with what code is running. I am not familiar with this particular windowing framework, but any I have worked with has had a separate thread for GUI and at least one for processing, to keep the GUI responsive, and message loops running in all active windows, not just the one currently with the focus. The modal dialog has no control over what code in other threads are executed when.
You should be able to break into the debugger and see what threads are running and what is running in each thread at any given time.
I've worked through the excellent Matplotlib GUI tutorial found at: http://blog.rcnelson.com/building-a-matplotlib-gui-with-qt-designer-part-1/. This program uses a QListWidget to select plots to show. Everything works correctly but I have one additional need. Once a item in the list is selected you can select the next or previous item with the arrow keys. The next or previous item is highlighted. What I want is a means to trigger the same event that is triggered by clicking. The click event is handled by the following code:
self.mplfigs.itemClicked.connect(self.changefig)
I've tried the following and neither works:
self.mplfigs.itemEntered.connect(self.changefig)
self.mplfigs.currentRowChanged.connect(self.changefig)
Much Google searching hasn't helped so any hints are very welcome.
You probably need to use itemSelectionChanged signal, in your case self.mplfigs.itemSelectionChanged.connect(self.changefig) should trigger the function, I don't have the full code but that should work and please take look here
Adding a minimal working example:
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys
class myListWidget(QListWidget):
def Clicked(self,item=None):
if not item:
item = self.currentItem()
QMessageBox.information(self, "ListWidget", "You clicked: "+item.text())
def main():
app = QApplication(sys.argv)
listWidget = myListWidget()
#Resize width and height
listWidget.resize(300,120)
listWidget.addItem("Item 1");
listWidget.addItem("Item 2");
listWidget.addItem("Item 3");
listWidget.addItem("Item 4");
listWidget.setWindowTitle('PyQT QListwidget Demo')
listWidget.itemSelectionChanged.connect(listWidget.Clicked)
listWidget.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
Original code is take from here
#Achayan got me very close. Here is what solved the problem. Using the following line is as was suggested:
self.mplfigs.itemSelectionChanged.connect(self.changefig)
I needed to change changefig from:
def changefig(self, item):
text = item.text()
self.rmmpl()
self.addmpl(self.fig_dict[text])
To:
def changefig(self, item=None):
if not item:
item = self.mplfigs.currentItem()
text = item.text()
self.rmmpl()
self.addmpl(self.fig_dict[text])
Unlike itemClicked, itemSelectionChanged doesn't emit the item so the extra if statement was needed to get the particular item necessary within changefig.
However, the following line of code seems to work without modifying changefig.
self.mplfigs.currentItemChanged.connect(self.changefig)
Evidently currentItemChanged emits the item like itemClicked does.
{Edit: the answer by Bryan Oakley in the suggested duplicate question enter link description here a) fires a response on change to the array variable (arrayvar.trace mode="w"), and I need it triggered on FocusOut, as described in my original question; b) works for Python 2, but I'm having trouble converting it to work in Python 3.5. I'm currently using his and pyfunc's answers as leads and trying to figure out a similar solution using a FocusOut event.}
I am working on a tkinter GUI that lets a user select a particular type of calculation, using a pair of radio button lists. Based on the selections, a tool bar is populated with multiple modular entry widgets, one for each variable the calculation requires. The goal is to have the numerical entry values passed to the model, which will return data to be graphed on a canvas or matplotlib widget.
My question is: what typical strategy is used for gathering and continually refreshing values from multiple widgets, in order to update displays and to pass them on to the model? The trick here is that there will be a large number of possible calculation types, each with their own toolbar. I'd like the active toolbar to be "aware" of its contents, and ping the model on every change to a widget entry.
I think the widgets and the toolbar would have to be classes, where the toolbar can query each widget for a fresh copy of its entry values when a change is detected, and store them as some collection that is passed to the model. I'm not entirely sure how it can track changes to the widgets. Using a "validate='focusout' " validation on the entry widget (e.g. as in
this validation reference )
suggests itself, but I already use "validate='key' " to limit all entries to numbers. I don't want to use "validate=all" and piggyback onto it because I don't want to continually ask the model to do a lengthy calculation on every keypress.
I'm new to GUI programming, however, so I may be barking up the wrong tree. I'm sure there must be a standard design pattern to address this, but I haven't found it.
Below is a screenshot of a mockup to illustrate what I want the GUI to do. The Task radiobutton controls which secondary button menu appears below. The selection in the second menu populates the top toolbar with the necessary entry widgets.
The following code does (mostly) what I want. The ToolBar frame objects will store the values from its contained widgets, and call the appropriate model as needed. The VarBox objects are Entry widgets with extra functionality. Hitting Tab or Return refreshes the data stored in the ToolBar dictionary, tells the ToolBar to send data to the model, and shifts focus to the next VarBox widget.
from tkinter import *
# Actual model would be imported. "Dummy" model for testing below.
def dummy_model(dic):
"""
A "dummy" model for testing the ability for a toolbar to ping the model.
Argument:
-dic: a dictionary whose values are numbers.
Result:
-prints the sum of dic's values.
"""
total = 0
for value in dic.values():
total += value
print('The total of the entries is: ', total)
class ToolBar(Frame):
"""
A frame object that contains entry widgets, a dictionary of
their current contents, and a function to call the appropriate model.
"""
def __init__(self, parent=None, **options):
Frame.__init__(self, parent, **options)
self.vars = {}
def call_model(self):
print('Sending to dummy_model: ', self.vars)
dummy_model(self.vars)
class VarBox(Frame):
"""
A customized Frame containing a numerical entry box
Arguments:
-name: Name of the variable; appears above the entry box
-default: default value in entry
"""
def __init__(self, parent=None, name='', default=0.00, **options):
Frame.__init__(self, parent, relief=RIDGE, borderwidth=1, **options)
Label(self, text=name).pack(side=TOP)
self.widgetName = name # will be key in dictionary
# Entries will be limited to numerical
ent = Entry(self, validate='key') # check for number on keypress
ent.pack(side=TOP, fill=X)
self.value = StringVar()
ent.config(textvariable=self.value)
self.value.set(str(default))
ent.bind('<Return>', lambda event: self.to_dict(event))
ent.bind('<FocusOut>', lambda event: self.to_dict(event))
# check on each keypress if new result will be a number
ent['validatecommand'] = (self.register(self.is_number), '%P')
# sound 'bell' if bad keypress
ent['invalidcommand'] = 'bell'
#staticmethod
def is_number(entry):
"""
tests to see if entry is acceptable (either empty, or able to be
converted to a float.)
"""
if not entry:
return True # Empty string: OK if entire entry deleted
try:
float(entry)
return True
except ValueError:
return False
def to_dict(self, event):
"""
On event: Records widget's status to the container's dictionary of
values, fills the entry with 0.00 if it was empty, tells the container
to send data to the model, and shifts focus to the next entry box (after
Return or Tab).
"""
if not self.value.get(): # if entry left blank,
self.value.set(0.00) # fill it with zero
# Add the widget's status to the container's dictionary
self.master.vars[self.widgetName] = float(self.value.get())
self.master.call_model()
event.widget.tk_focusNext().focus()
root = Tk() # create app window
BarParentFrame = ToolBar(root) # holds individual toolbar frames
BarParentFrame.pack(side=TOP)
BarParentFrame.widgetName = 'BarParentFrame'
# Pad out rest of window for visual effect
SpaceFiller = Canvas(root, width=800, height=600, bg='beige')
SpaceFiller.pack(expand=YES, fill=BOTH)
Label(BarParentFrame, text='placeholder').pack(expand=NO, fill=X)
A = VarBox(BarParentFrame, name='A', default=5.00)
A.pack(side=LEFT)
B = VarBox(BarParentFrame, name='B', default=3.00)
B.pack(side=LEFT)
root.mainloop()
In my new application I want when the mouse is over the entry() widget to change color (this I know how to do it) but I want the color to change gradually, not immediately.
This is my code:
# User_Line Focus In/Out
def User_Line_Focus_In(self, event):
self.User_Line.configure(bg = "#DCDCDC")
def User_Line_Focus_Out(self, event):
self.User_Line.configure(bg = "#FFFFFF")
You need to create a method which increments the colour and you need to use tkinter's after which registers an alarm callback that is called after a given time. You then need to reference it recursively in order to get the fading effect you want.
def incrementHex(hex_str, increment): #with hex_str in format "#FFFFFF" or any colour
red = int(hex_str[1:3],16) #specifies base for integer conversion
green = int(hex_str[3:5],16)
blue = int(hex_str[5:],16)
red += increment #increment can be negative
green += increment
blue += increment
new_hex_str = "#" + str(hex(red)) + str(hex(blue)) + str(hex(green))
return new_hex_str
def Fade(self, start_hex, increment):
new_hex = self.incrementHex(start_hex, increment)
self.User_Line.configure(bg = new_hex)
#where self.master is the parent widget as defined in the __init__ method...
self.master.after(50,lambda: self.Fade(new_hex, increment)) #or any time interval in milliseconds
#you'll probably need some code to stop it fading here, but I'll let you tackle that one :)
def User_Line_Focus_In(self, event):
self.Fade("#FFFFFF",-1) #could be any colour and increment
I haven't been able to test it, but I think it should work in principle. An extension of this would be to have different increments for red, green and blue.
I think you are going to have to pull up your socks on this one and do some coding (tkinter doesn't have this built in)
So what you are looking for is :
An algorithm to go from color one to color two and get intermediate colors. (Hex values are just numbers in base 16 but they can be added or subtracted like normal numbers)
The simplest solution would be to just run the algorithm (color_difference here)
def fade_colors(event, new_color):
old_color = event.widget.cget('bg')
for color in color_difference(old_color, new_color):
event.widget.configure(color)
time.sleep(0.1)
widget.bind('<Enter>', lambda event: fade_colors(event, color))
You might also like to cancel the operation if the user leaves the widget. Take a look at the built in sched module.
If you find your gui becomes unresponsive during the fading you could consider using the after method, you can read this excellent blog post on non blocking gui techniques in python and tkinter. This may not be an issue if you cancel the callback as soon as the user leaves the widget (thus freeing up tkinter to handle his other actions)
I'm very new to threading am and still trying to get my head around how to code most of it. I am trying to make what is effectively a text editor-type input box and so, like every text editor I know, I need a cursor-bar thing to indicate the location at which the text is being typed to. Thus I also want to be able to flicker/blink the cursor, which i thought would also prove good practice for threading.
I have a class cursor that creates a rectangle on the canvas based on the bounding box of my canvas text, but I then need to change it's location as more characters are typed; stop the thread and instantaneously hide the cursor rectangle when the user clicks outside of the input box; and lastly restart the thread/a loop within the thread (once again, sharing a variable) - the idea here being that the cursor blinks 250 times and after then, disappears (though not necessary, I thought it would make a good learning exercise).
So assuming that I have captured the events needed to trigger these, what would be the best way to go about them? I have some code, but I really don't think it will work, and just keeps getting messier. My idea being that the blinking method itself was the thread. Would it be better to make the whole class a thread instead? Please don't feel restricted by the ideas in my code and feel free to improve it. I don't think that the stopping is working correctly because every time I alt+tab out of the window (which i have programmed to disengage from the input box) the Python shell and tkinter GUI stop responding.
from tkinter import *
import threading, time
class Cursor:
def __init__(self, parent, xy):
self.parent = parent
#xy is a tuple of 4 integers based on a text object's .bbox()
coords = [xy[2]] + list(xy[1:])
self.obj = self.parent.create_rectangle(coords)
self.parent.itemconfig(self.obj, state='hidden')
def blink(self):
blinks = 0
while not self.stop blinks <= 250:
self.parent.itemconfig(self.obj, state='normal')
for i in range(8):
time.sleep(0.1)
if self.stop: break
self.parent.itemconfig(self.obj, state='hidden')
time.sleep(0.2)
blinks += 1
self.parent.itemconfig(self.obj, state='hidden')
def startThread(self):
self.stop = False
self.blinking = threading.Thread(target=self.blink, args=[])
self.blinking.start()
def stopThread(self):
self.stop = True
self.blinking.join()
def adjustPos(self, xy):
#I am not overly sure if this will work because of the thread...
coords = [xy[2]] + list(xy[1:])
self.parent.coords(self.obj, coords)
#Below this comment, I have extracted relevant parts of classes to global
#and therefore, it may not be completely syntactically correct nor
#specifically how I initially wrote the code.
def keyPress(e):
text = canvas.itemcget(textObj, text)
if focused:
if '\\x' not in repr(e.char) and len(e.char)>0:
text += e.char
elif e.keysym == 'BackSpace':
text = text[:-1]
canvas.itemconfig(textObj, text=text)
cursor.adjustPos(canvas.bbox(textObj))
def toggle(e):
if cursor.blinking.isAlive(): #<< I'm not sure if that is right?
cursor.stopThread()
else:
cursor.startThread()
if __name__=="__main__":
root = Tk()
canvas = Canvas(root, width=600, height=400, borderwidth=0, hightlightthickness=0)
canvas.pack()
textObj = canvas.create_text(50, 50, text='', anchor=NW)
root.bind('<Key>', keyPress)
cursor = Cursor(canvas, canvas.bbox(textObj))
#Using left-click event to toggle thread start and stop
root.bind('<ButtonPress-1', toggle)
#Using right-click event to somehow restart thread or set blinks=0
#root.bind('<ButtonPress-3', cursor.dosomething_butimnotsurewhat)
root.mainloop()
If there is a better way to do something written above, please also tell me.
Thanks.