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Safari | Python Developer's Handbook -> Designing Applications





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Designing Applications

Up to this point, we've seen how to handle the properties and methods of Tkinter's widgets. Now, we will learn the basic steps to write real-world applications.

Tkinter is really powerful, and if you are not satisfied with the widgets that it offers, you can create your own set of widgets. A very interesting and customized widget that you should consider checking before learning how to create your own, is the TreeWidget, which is part of the latest idle distribution. This widget uses a Tk Canvas widget and some images to nicely simulate the TreeView Windows control.

The simplest windowing application that you can create consists of just one window, which is called the root window. The root window is created using the Tk() call.

					
from Tkinter import *
root = Tk()
root.mainloop()

				

If your application needs more than just one single window, you can use the Toplevel widget to create additional windows for you. This widget has a behavior very similar to the window generated by Tk(). This widget also dispenses the use of geometry management functions because the window manager displays this widget, immediately after you call it.

					
from Tkinter import *
def mywindow():
    top = Toplevel(root)

root = Tk()
b1 = Button(root, text="Create new window", command=mywindow)
b1.pack()
root.mainloop()

				

After adding a lot of windows to your application, maybe now you are wondering whether it would be OK to add a menu to your program. The following code does that for you.

					
from Tkinter import *
import sys
def newwindow():
    top = Toplevel(root)
def aboutwindow():
    who = Toplevel(root)
    Label(who, text="This is the about window").pack()

root = Tk()
menu = Menu(root)
root.config(menu=menu)

filemenu = Menu(menu)
menu.add_cascade(label="File", menu=filemenu)
filemenu.add_command(label="New", command=newwindow)


filemenu.add_separator()
filemenu.add_command(label="Exit", command=sys.exit)

helpmenu = Menu(menu)
menu.add_cascade(label="Help", menu=helpmenu)
helpmenu.add_command(label="About...", command=aboutwindow)

root.mainloop()

				

What's next? What about adding a toolbar to our little application? The simplest way to implement a toolbar is by taking a Frame widget and storing all the required buttons on it.

					
from Tkinter import *
import sys
def newwindow():
    top = Toplevel(root)
def aboutwindow():
    who = Toplevel(root)
    Label(who, text="This is the about window").pack()

root = Tk()
menu = Menu(root)
root.config(menu=menu)

filemenu = Menu(menu)
menu.add_cascade(label="File", menu=filemenu)
filemenu.add_command(label="New", command=newwindow)
filemenu.add_separator()
filemenu.add_command(label="Exit", command=sys.exit)

helpmenu = Menu(menu)
menu.add_cascade(label="Help", menu=helpmenu)
helpmenu.add_command(label="About...", command=aboutwindow)

toolbar = Frame(root)
newimage = PhotoImage(file="new.gif")
b1 = Button(toolbar, image=newimage, width=16, command=newwindow)
b1.pack(side=LEFT, padx=1, pady=1)
helpimage = PhotoImage(file="help.gif")
b2 = Button(toolbar, image=helpimage, width=16, command=aboutwindow)
b2.pack(side=LEFT, padx=1, pady=1)
toolbar.pack(side=TOP, fill=X)
root.mainloop()

				

As we want our toolbar to be on the highest area of our screen, we have to pack it on the top side of the Frame widget. The fill option being set to X in the toolbar widget enables the toolbar to extend itself, covering the entire extension of the parent frame size.

Note the usage of the PhotoImage class. This class is used to load the GIF files from disk and store them into variables. Then, these variables are passed to the Button options that handle images.

Let's move forward now. The next step is to create a status bar for our small application. We want this bar to be on the bottom side of the window.

					
from Tkinter import *
import sys
def newwindow():
    top = Toplevel(root)
    statusbar.config(text="This is a testing application.")

def aboutwindow():
    who = Toplevel(root)
    Label(who, text="This is the about window").pack()
    statusbar.config(text="Hi There!")

root = Tk()
menu = Menu(root)
root.config(menu=menu)

filemenu = Menu(menu)
menu.add_cascade(label="File", menu=filemenu)
filemenu.add_command(label="New", command=newwindow)
filemenu.add_separator()
filemenu.add_command(label="Exit", command=sys.exit)

helpmenu = Menu(menu)
menu.add_cascade(label="Help", menu=helpmenu)
helpmenu.add_command(label="About...", command=aboutwindow)

toolbar = Frame(root)
newimage = PhotoImage(file="new.gif")
b1 = Button(toolbar, image=newimage, width=16, command=newwindow)
b1.pack(side=LEFT, padx=1, pady=1)
helpimage = PhotoImage(file="help.gif")
b2 = Button(toolbar, image=helpimage, width=16, command=aboutwindow)


b2.pack(side=LEFT, padx=1, pady=1)
toolbar.pack(side=TOP, fill=X)

statusbar = Label(root, text="This is a testing application.", bd=1,
 relief=SUNKEN, anchor=W)
statusbar.pack(side=BOTTOM, fill=X)

				

As you could see, we used the Label widget to implement the statusbar in order to be able to change the text value later. Pretty nice, isn't it?

Now, have a look at the final shape of our interface (Figure 15.16).

Figure 15.16. This figure shows the complete example of designing the structure of an application using Tkinter.
graphics/15fig16.gif

In my opinion, one of the greatest things about designing GUI applications using Tkinter is the number of things that are already done and ready to be used by your applications. Some examples are the following modules, which are part of the Tkinter distribution, and implement common dialog boxes.

tkMessageBox This module implements the classic Yes/No and Abort/Retry/Ignore dialog styles.

tkSimpleDialog This module implements a base class that can be used to implement other modules.

tkFileDialog This module implements a file dialog, which is very close to ... ... (Not finished, please download and read the complete file)

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