We Keep Coding

Python Tkinter - How do I change variables from outside the main window class?

Now i understand the concept of instance variables and classes, I've never had a problem with them before and I use them frequently. However when I make my MainWindow class, everything is peachy until i try accessing instance variables.
http://pastebin.com/tDs5EJhi is the full code, but at this point it's just placing labels and frames and whatnot, no actual logic is going on. The window looks fine and nothing bad happens.
My question comes to be when I try changing things inside of the window externally. I figured I could just make an instance of the class and change variables from there (namely instancevariable.ImageCanvas.itemconfig()) like i can normally, but Tkinter isn't being nice about it and I think it's a result of Tkinter's mainloop().
Here's the tidbit of my class MainWindow() that i'm having trouble with (ln 207)
...
self.C4 = Tk.PhotoImage(file="temp.png")
self.card4 = self.CardCanvas.create_image(120,46,image=self.C4, state=Tk.NORMAL)
#self.CardCanvas.itemconfig(4, state=Tk.HIDDEN) # < It works here
...
self.root.mainloop()
window = MainWindow()
window.CardCanvas.itemconfig(4, state=Tk.HIDDEN) # < It doesn't work here
That's how i learned how to edit instance variables. When the window pops up, the itemconfig command doesn't actually apply like it would were it inside the class (or maybe it did and the window just didn't update?) and after closing the window I get this error:
_tkinter.TclError: invalid command name
which I assume is just because it's trying to apply a method to variables that don't exist anymore, now that the window has closed.
So I guess here's my big question - I have a MainWindow class, and from what I can tell, nothing can be changed from outside of the class because the Tk.mainloop() is running and won't stop to let other code after it run, like the itemconfig. How do I go about changing those variables? Code after the instance variable declaration doesn't seem to run until the MainWindow() is closed.

You are correct that code after mainloop doesn't run. It does, but only after the GUI has been destroyed. Tkinter is designed for the call to mainloop be the last (or very nearly last) line of executable code. Once it is called, all other work must be done as reaction to events. That is the essence of GUI programming.
The answer to "how do I go about changing the variables" is simple: do it before you call mainloop, or do it in reaction to an event. For example, do it in a callback to a button, do it in a function bound to an event, or to a time-based event via after, and so on.

Multiple windows in PyQt4?

I've just begun using pyqt4. I followed a tutorial (http://zetcode.com/tutorials/pyqt4/)
One thing that puzzles me is this part:
def main():
app = QtGui.QApplication(sys.argv)
ex = GUI()
sys.exit(app.exec())
And the reason for this I explain here:
I have made a small program that opens four more windows except for the first main window.
So I tried to replicate what I saw worked with main-window and created a class for every new window and tried to do like with the above. Currently it looks like this:
def main2():
#app = QtGui.QApplication(sys.argv)
ex2 = Settings()
sys.exit(app.exec())
As you can see I have modified it. If I left the first line in the function uncommented the program would crash. I tried to do without the sys.exit(app.exec_())-part but that would only make the new window close milliseconds after it showed.
This way though, everything runs and works. Only that in the command window, an error message displays. I don't know how to fix this, since I cannot remove the last line, and I dont't know what to replace "app" with.
I know I'm probably doing the new windows wrong from the beginning, but I don't know how to make these windows open from the original window in any other way. I haven't been able to get anything else to work, and this at least runs and works right now. So the only problem is error messages in the prompt, it would be nice to get rid of them :)
Thanks for any help (complicated and easy ones)!
Forgot to mention, I made the classes start like this:
class GUI(QtGui.QMainWindow):
def __init__(self):
super(GUI, self).__init__()
self.initUI()
and
class Settings(QtGui.QWidget):
def __init__(self):
super(Settings, self).__init__()
...here goes some more...
self.initUI2()
and I open Settings-window by calling main2()

You must create one and only one QApplication in your program.
Keep in mind that GUI programming is event-driven, you first declare widgets and then run the main loop with app.exec(), when the user quit your application, app.exec() returns.
The QApplication purpose is to handle user events and propagate them to your code with Qt signals. I suggest you check Qt documentation, it's very complete, even if it's targetting C++ programmers.
So for instance, a way to create two widgets would be:
def main():
app = QtGui.QApplication(sys.argv)
ex = QtGui.QWidget()
ex.show()
ex2 = QtGui.QWidget()
ex2.show()
sys.exit(app.exec())

Destroyed about dialog doesn't reappear properly

I'm working on a GUI application in Python / Glade, and have the following issue.
I am trying to get an About dialog properly working...however when I click 'Close' (in the About dialog) and then attempt to open it again, this is all I see:
So, just a tiny little snippet of the window, and a non-functioning close button.
This is my class for my Glade window:
# glade object
class MainWindow(object):
builder_ = None
# load main window
def __init__(self):
handler = {
"sigWindowDestroy" : gtk.main_quit,
"sigShowAbout" : self.show_about
}
projfile = "proj.glade"
self.builder_ = gtk.Builder()
self.builder_.add_from_file(projfile)
self.builder_.connect_signals(handler)
window = self.builder_.get_object("main_window")
window.show()
# show about dialog
def show_about(self, *args):
dAbout = self.builder_.get_object("dAbout")
dAbout.run()
dAbout.destroy()
And in my main function:
# load glade gui
app = MainWindow()
gtk.main()
On the second click, I see the following output in my terminal window (using Mac OS X).
GtkWarning: gtk_widget_show: assertion `GTK_IS_WIDGET (widget)' failed
dAbout.run()
GtkWarning: gtk_label_set_markup: assertion `GTK_IS_LABEL (label)' failed
dAbout.run()
Edit: sorry, must reopen for general unfamiliarity with PyGTK.
I've used the show()/hide() methods instead of run()/destroy() as proposed. Now, I was following along with another SO post, which highlighted this tutorial (who said to use run()/destroy()), and am seeing this behavior.
First, the Close button does nothing. I had thought for some reason its behavior was pre-defined.
Second, closing the dialog with the corner close button still provides the same behavior that I see with run()/destroy() as above.
Edit 2: Solved by adding the following:
dAbout.connect("response", lambda d, r: d.hide())

Don't try to (deep-)copy a widget. It doesn't work, as you found out.
Instead, hide() the dialog instead of destroy()ing it.

You could have even used run(). You just shouldn't use destroy(). What made you think, you shouldn't use run() and hide() together? See, when you destroy a widget, that means removing it from memory as if it never had been build. If you hide it, you can reuse it later, but take care of changes a user might have done to it, as the window will re-appear in the state it was in before being hidden. You can manipulate a widgets properties from code while hidden.
The "predefined" action of your close button was caused by run(). The solution you posted, using the lambda function is little more than what run() does for you. Basically it does the following:
Connect the "response" signal of your DialogWindow
Connect the "delete-event" signal of your DialogWindow
Start a new Gtk main loop to block the application
Show your widget
Disconnect the signals
Return the response
You just need to hide() it afterwards and are able to run() it again.

tk destroy() and grid_forget() don't always work

i'm hoping anyone can help me out here. i'm having an issue with a tkinter gui i built. the issue only happens in windows. My GUI creates a results frame with some labels in it, when it's time to calculate something else, the user clicks on the "newPort" button and that button is supposed to remove the results frame and set to False some instance attributes internal to the calculation. The issue i'm having, which is apparent only in windows is that sometimes the results frame, and its descendant labels don't disappear every time. Sometimes they do, sometimes they don't. The instance variable is correctly set to False but the widgets are still visible on the main GUI. The GUI also contains a couple checkboxes and radiobuttons but they don't impact the creation of the results frame nor its expected destruction. I have not been able to pin point a pattern of actions the user takes before clicking on the newPort button which causes the frame and labels to not get destroyed. This happens when i freeze my app with py2exe, as well as running the app from the python interpreter within the eclipse IDE. I have not tried running the app from the python interpreter directly (i.e. without the IDE) and this problem does not happen on my Mac when i run the app using the eclipse python interpreter. Thanks very much all! My code looks like this:
import Tkinter as TK
class widget(object):
def __init__(self,parent=None):
self.parent = TK.Frame(parent)
self.parent.grid()
self.frame = TK.Frame(self.parent)
self.frame.grid()
newLedger = TK.Button(self.parent,command=self.newPort).grid()
self.calcButton = TK.Button(self.frame,command=self.showResults)
self.calcButton.grid()
self.calcVariable = True
def newPort(self):
self.calcVariable = False
try:
self.second.grid_forget()
self.first.grid_forget()
self.resultsFrame.grid_forget()
self.second.destroy()
self.first.destroy()
self.resultsFrame.destroy()
except:
raise
self.frame.update_idletasks()
def showResults(self):
self.resultsFrame = TK.Frame(self.frame)
self.resultsFrame.grid()
self.first = TK.Label(self.resultsFrame,text='first')
self.first.grid()
self.second = TK.Label(self.resultsFrame,text='second')
self.second.grid()
if __name__ == '__main__':
root = TK.Tk()
obj = widget(root)
root.mainloop()

You don't need to destroy or call grid_forget on the labels, and you don't need to call grid_forget on the resultsFrame; when you destroy the resultsFrame it will cause all off its children to be destroyed, and when these widgets are destroyed they will no longer be managed by grid.
The only way I can get widgets to not be destroyed is if I click on the "calc" button twice in a row without clicking on the "new" button in-between. I'm doing this by running your program from the command line.

How to make an arbirtary number of windows using Python and Tkinter?

I'm writing an app that doesn't have a main window (it runs inside a Python interpreter in another app), and I thought I had a good solution for getting Tkinter to cooperate--I made the Tkinter.Tk class into a Borg.
class RootWindow(Tk):
""" Invisible window that serves as the default parent
of all others.
"""
groupDict = {}
def __init__(self):
self.__dict__ = self.groupDict
if self.__dict__ == {}: # first instance
Tk.__init__(self)
self.withdraw()
Then I have my Windows, which are subclassed from Tkinter.Toplevel, default to parent=RootWindow(). The result should be that I can create any number of Windows and they'll use the same root.
It works once fine for the first Window, but after that things get all messed up. :(
see pic
What am I doing wrong? Is this even a feasible solution?
Thanks
EDIT: I should add that even though there's other stuff running in the picture, the problem can be duplicated just by using RootWindow as the parent of a Tkinter.Toplevel.
EDIT: I overrode Window.mainloop so everything uses the RootWindow event loop.
def mainloop(self):
self.master.wait_window(self)
Then I create each visible window like this:
test = Window()
test.mainloop()
It seems to work because the windows do show up, but their contents are packed in an odd way that's hard to describe. It alternates between no contents at all and having everything squished horizontally and expanded vertically.

One problem appears to be that you are forgetting to start the event loop. Or, based on further edits of your question, you may be starting more than one main loop. You need exactly one main loop that is run from the root window.
Tkinter certainly allows an arbitrary number of top level windows, but your question doesn't appear to have enough details to show what is wrong unless my first guess is correct.