GUI Programming in Python For Beginners: Create a Timer in 30 Minutes
Saving Absent-Minded Geeks From Soggy Gardens and Burned Food
Akkana Peck
Thursday, March 26, 2009 11:54:38 AM
Python programming is all the rage, because the language has such
simple, clean syntax, is easy to learn and has lots of libraries
available. But best of all, you're not limited to writing
command-line applications. Python has at least four ways to
make graphical apps, but today I'll concentrate on one: TkInter.
TkInter isn't necessarily the most powerful of the Python windowing
packages, but it's well supported on all operating systems. You can
give your application to your Windows- and Mac-using friends and
they'll be able to run it, as long as they have Python installed.
On Linux, though, you may have to install it: on Ubuntu or Debian
the package is named python-tk, while in Fedora it's tkinter.
For a project, start with a simple one. How about an "eggtimer"?
I'm always forgetting that I have cornbread baking in the oven,
or that I turned on the sprinklers in the garden. I need something
to remind me.
Let's start with a very simple Tkinter program. Paste the following into
your editor of choice (vim, emacs, kate, leafpad or whatever) and
write it to a file named, say, eggtimer:
#!/usr/bin/env python
from Tkinter import *
root = Tk()
button = Button(root, text="Hello", command=quit)
button.pack()
root.mainloop()
You can run your script by typing:
python eggtimer
or, if you make the file executable (see the
shell
scripting article), you can run it just by typing
eggtimer or double-clicking it from your file manager.
(Figure 1, Listing 1.)
Adding controls
Okay, a single button isn't so useful. For a timer, you need to be
able to set when it will alert you. And for that, a Scale
is a good choice. It gives you a slider you can use to choose
how many minutes you want your timer to wait. Add these two lines
to your script right before the line where you create your button:
scale = Scale(root, from_=1, to=45, orient=HORIZONTAL, length=300)
scale.pack()
from_ and to set the scale's low and high bounds.
Notice the underscore on the end of from_:
from without an underscore is a keyword in Python
so Tkinter isn't allowed to use it.
orient=HORIZONTAL makes the slider horizontal, and
length=300 sets it to 300 pixels wide.
Figure 2 (and Listing 2) shows the window with the Scale widget added.
Of course, Tkinter has other controls (called widgets) besides Scale.
Other Stories on LinuxPlanet
|
You can make an Entry if you want to read in a text string (or type
in the number of minutes), a Checkbutton or Radiobutton to set
yes/no options or other binary options, or a Text widget to
let the user enter a lot of text (more than one line).
You can also add controls to make things look nicer. For instance,
you can add a Label just before you create the Scale, to specify that
the slider means a time in minutes:
minutes = Label(root, text="Minutes:")
minutes.pack(side=LEFT)
Figure 3 shows what the window looks like now, and Listing 3 has the code.
======================================================
# Listing 1
#!/usr/bin/env python
from Tkinter import *
root = Tk()
button = Button(root, text="Start timing", command=quit)
button.pack(side="left")
root.mainloop()
======================================================
======================================================
# Listing 2
#!/usr/bin/env python
from Tkinter import *
root = Tk()
scale = Scale(root, from_=1, to=45, orient=HORIZONTAL)
scale.pack()
button = Button(root, text="Start timing", command=quit)
button.pack()
root.mainloop()
======================================================
======================================================
# Listing 3
#!/usr/bin/env python
from Tkinter import *
root = Tk()
minutes = Label(root, text="Minutes:")
minutes.pack(side=LEFT)
scale = Scale(root, from_=1, to=45, orient=HORIZONTAL, length=300)
scale.pack()
button = Button(root, text="Start timing", command=quit)
button.pack()
root.mainloop()
======================================================
Next: Packing Them In »
