1. CISC101 Reminders Grading of Quiz 4 underway.
Winter 2018 CISC101
9/20/2018
CISC101 Reminders
Grading of Quiz 4 underway.
Last assignment due Friday. We have covered everything you need to know for the assignment.
Winter 2018
CISC101 - Prof. McLeod
Prof. Alan McLeod

2. Today GUI Construction With tkinter, Cont.: Next time: Widget Options.
More about Buttons.
Colours.
tkinter Dialogs.
The Entry Widget.
Coupling and Binding…
Next time:
Radiobutton and Canvas Widgets.
Bears Demo.
More Python tools and modules.
Winter 2018
CISC101 - Prof. McLeod

3. Widget Options
widget_name.keys() gives you a list of dictionary keys, each of which is an option that can be changed for that widget.
Any set of these keys can be set when you create the widget. Or you just accept the default values.
widget_name.configure() (no parameters) gives you a list of the keys and their values (a dictionary).
Winter 2018
CISC101 - Prof. McLeod

4. Widget Options, Cont.
widget_name.cget(option) gives the value of the specified option as a string.
widget_name.configure(option=?, option=?, …) allows you to change as many options as you want all at once.
You can shorten .configure to just .config.
You can treat the widget as a dictionary if you are only getting or setting a single property (use [ ]).
Winter 2018
CISC101 - Prof. McLeod

5. Button Widget, Cont. See ButtonDemo.py:
Binding a keypress event to the window.
Jazzing up the button.
The keypress binding can only have the event object. See the help docs for all the event members that you can use.
Winter 2018
CISC101 - Prof. McLeod

6. Virtual Events
You can combine events to a single virtual event, for convenience.
See ButtonDemoV2.py
Winter 2018
CISC101 - Prof. McLeod

7. Colours!
The colour of anything can be changed – the window background, the widget background and the foreground (often the text).
Colours are specified using a name known to tkinter or the RGB system: “Red Green Blue”.
Winter 2018
CISC101 - Prof. McLeod

8. CISC101
Colours, Cont.
We have specified colours manually using “#RRGGBB” as a string.
You can also specify or save colours as a three element tuple, with the three intensity levels.
The intensity of each colour lies between 0x00 and 0xFF, or 0 and 255 (one byte).
Possible range of 256*256*256 = 16,777,216 colours (called “24 bit colour”).
(Windows uses 32 bit colour, where the extra byte is used to specify transparency.)
Winter 2018
CISC101 - Prof. McLeod
Prof. Alan McLeod

9. Colours, Cont.
This demo program is also using a colour chooser dialog box called tkinter.colorchooser
This is a GUI window that has already been constructed for us.
(We have used this dialog with a turtle demo before…)
See Window8.py.
Winter 2018
CISC101 - Prof. McLeod

10. CISC101
Other Dialog Boxes
tkinter.commondialog - Base class for the dialogs defined in the other modules listed here.
tkinter.filedialog - Common dialogs to allow the user to specify a file to open or save.
tkinter.messagebox - Access to standard Tk dialog boxes.
tkinter.simpledialog - Basic dialogs and convenience functions.
Winter 2018
CISC101 - Prof. McLeod
Prof. Alan McLeod

11. tkinter.filedialog Use this to get a filename.
Much easier than getting the user to try typing in a filename, let alone a path!
See Window9.py.
Winter 2018
CISC101 - Prof. McLeod

12. Other Dialog Boxes, Cont.
tkinter.messagebox defines various “ask” and “show” dialogs: askokcancel, askquestion, askretrycancel, askyesno, showerror, showinfo, showwarning.
See Window10.py
Also note the “Quit” button. This will only work properly if the program is run outside of IDLE. (Type “python window10.py” at a command prompt, for example). Or:
Winter 2018
CISC101 - Prof. McLeod

13. Running a tkinter Program
When debugging it helps to run your program from inside IDLE where you can see error messages being displayed to the shell window (or “console”).
But if you double-click on a tkinter *.py program an annoying DOS (or “command”) window shows up and goes away. And the top.quit command does not work. yuk.
Make a copy of your program with the extension *.pyw.
Winter 2018
CISC101 - Prof. McLeod

14. Running a tkinter Program, Cont.
This associates your program with Pythonw.exe rather than the normal Python.exe program.
Now it will run without the annoying DOS window if you run it from Windows Explorer, for example.
But, you won’t see any console error messages.
Winter 2018
CISC101 - Prof. McLeod

15. Other Dialog Boxes, Cont.
tkinter.simpledialog defines askinteger(title, prompt, initialvalue, minvalue, maxvalue), askfloat and askstring.
See Window11.py
Note behaviour if illegal value supplied!
Winter 2018
CISC101 - Prof. McLeod

16. CISC101
Entry Widget
Allows the user to provide information to your program by typing it into the text box.
Specify a width (width=?), in characters, in addition to the master and the font, as a minimum when you create one.
Use the get() method on the Entry widget to get the contents – returned as a string only.
See Window12.py
Winter 2018
CISC101 - Prof. McLeod
Prof. Alan McLeod

17. Coupling a Variable to a Widget
You can couple a variable to an Entry widget (for example) so that when the variable changes the text in the entry box changes, or if you change the text in the entry box the contents of the variable changes.
Use StringVar(), IntVar(), DoubleVar(), or BooleanVar().
Use the “textvariable” property to couple the variable to the widget.
Winter 2018
CISC101 - Prof. McLeod

18. Variable Coupling, Cont.
Generate the coupled variable:
contents = tkinter.StringVar()
Couple variable to entry widget:
textEntry = tkinter.Entry(…, textvariable=contents)
Setting variable changes entry contents, too:
contents.set("Hello")
Get the variable contents with:
contents.get()
Winter 2018
CISC101 - Prof. McLeod

19. Clean Up Window12.py
Make it so the result label empties out if the input number changes.
Make it keyboard responsive:
<Enter> should calculate the result.
<Esc> should close the window.
See Window12C.py (or Window12C.pyw).
Winter 2018
CISC101 - Prof. McLeod

20. widget.bind(key name(s), function)
Bindings
Use the .bind method invoked from the widget:
widget.bind(key name(s), function)
Now, when the widget has the focus, the key press will run the named function.
You can bind functions to the entire window, as well – then it does not matter which widget has the focus.
has a list of key names.
Winter 2018
CISC101 - Prof. McLeod