Adding python functionality to Tkinter front end

Question

This is the front end I developed for my application using Tkinter:

from Tkinter import *
class Example(Frame):
def __init__(self, parent):
    Frame.__init__(self, parent)   
    self.parent = parent
    self.initUI()

def initUI(self):

    self.parent.title("Simple")
    self.pack(fill=BOTH, expand=1)

    frame = Frame(self, relief="flat", borderwidth=1)

    label=Label(frame,text="Scope:")
    label.pack(side="left", fill=None, expand=False)

    var = StringVar()
    var.set("today")
    list = OptionMenu(frame, var, "today","yesterday","this week","last week","this month","last month")
    list.pack(side="left", fill=None, expand=False)

    fetchButton = Button(frame, text="Fetch",command=self.handle(var))
    fetchButton.pack(side="left", fill=None, expand=False)

    frame.grid(row=1,column=1,pady=4,padx=5,sticky=W)

    area = Text(self,height=15,width=60)
    area.grid(row=2,column=1,rowspan=1,pady=4,padx=5)

    scroll = Scrollbar(self)
    scroll.pack(side=RIGHT, fill=Y)

    area.config(yscrollcommand=scroll.set)
    scroll.config(command=area.yview)
    scroll.grid(row=2, column=2, sticky='nsew')

    quitButton = Button(self, text="Cancel",command=self.quit)
    quitButton.grid(pady=4,padx=5,sticky=W,row=3, column=1)

root = Tk()
app = Example(root)
root.mainloop()

Where exactly do I have to put the handle() method so it can write repeatedly to the text widget? When I put handle() within the Example class and use self.area.insert(), it shows an error saying

Example instance has no attribute 'area'

Please help out.

ebarr · Accepted Answer · 2014-03-17 12:02:57Z

1

You need to pass the function object to the Button instance, not a function call. i.e.

fetchButton = Button(frame, text="Fetch",command=self.handle)

To make the handle work in the context of the rest of the code:

from Tkinter import *

class Example(Frame):
    def __init__(self, parent):
        Frame.__init__(self, parent)
        self.parent = parent
        self.parent.title("Simple")
        self.pack(fill=BOTH, expand=1)
        self.init_ui()

    def init_ui(self):
        self.frame = Frame(self, relief="flat", borderwidth=1)
        self.frame.grid(row=1,column=1,pady=4,padx=5,sticky=W)
        self.label=Label(self.frame,text="Scope:")
        self.label.pack(side="left", fill=None, expand=False)

        self.var = StringVar()
        self.var.set("today")

        self.list = OptionMenu(self.frame, self.var, "today","yesterday",
                               "this week","last week","this month",
                               "last month")
        self.list.pack(side="left", fill=None, expand=False)

        self.fetchButton = Button(self.frame, text="Fetch",command=self.handle)
        self.fetchButton.pack(side="left", fill=None, expand=False)

        self.area = Text(self,height=15,width=60)
        self.area.grid(row=2,column=1,rowspan=1,pady=4,padx=5)

        self.scroll = Scrollbar(self)
        self.scroll.pack(side=RIGHT, fill=Y)

        self.area.config(yscrollcommand=self.scroll.set)
        self.scroll.config(command=self.area.yview)
        self.scroll.grid(row=2, column=2, sticky='nsew')

        self.quitButton = Button(self, text="Cancel",command=self.quit)
        self.quitButton.grid(pady=4,padx=5,sticky=W,row=3, column=1)

    def handle(self):
        self.area.delete(1.0, END)
        self.area.insert(CURRENT,self.var.get())

if __name__ == "__main__":
    root = Tk()
    app = Example(root)
    root.mainloop()

Declaring your widgets as attributes will save you a lot of pain an suffering as your application expands. Also keeping references to everything in Tk can stop some unwanted garbage collection, particularly with images in Label instances.

It is also worth noting that using grid and pack interchangeably is likely to lead to bugs later on.

edited Mar 17, 2014 at 12:02

answered Mar 17, 2014 at 11:35

ebarr

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4 Comments

ebarr Over a year ago

The reason you were getting that error is because you did not declare area as an attribute. If you change all your area instances to self.area, this will solve the problem.

raul Over a year ago

Thanks, works cool. But my handle() method contains some heavy functionality and it takes at least 5 mins for the first self.area.insert() to be called. When I click on the window in the meantime, the title bar shows Not Responding and the whole window goes gray. Some way to handle that?

raul Over a year ago

looks like I have to use multithreading to tackle Not Responding. thanks anyway.

ebarr Over a year ago

Yep, sounds like you need to spawn the handle method in a new thread.

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