1. Computer Science 111 Fundamentals of Programming I Text Areas
Radio Buttons and Check Buttons
Prompter Boxes
Working with Colors

2. class TaxCode(EasyFrame):
"""Application window for the tax calculator."""
RATE = .15
EXEMPTION_AMOUNT =
def __init__(self):
"""Sets up the window and the widgets."""
EasyFrame.__init__(self, title = "Tax Calculator")
. . .
# The event handling method for the button
def computeTax(self):
"""Obtains the data from the input fields and uses
them to compute the tax, which is sent to the
output field."""
income = self.incomeField.getNumber()
exemptions = self.exField.getNumber()
tax = max(0.0,
(income - exemptions * TaxCode.EXEMPTION_AMOUNT) \
* TaxCode.RATE)
self.taxField.setNumber(tax)

3. Widgets for Text I/O
A text field (class TextField) is used for the I/O of one-line strings
A text area (class TextArea) is used for the I/O of multiple lines of text
See the breezypythongui site for details

4. Example: A Simple Text File Editor
Shows a text area to view and edit the contents of a text file
Includes command buttons for opening and saving a file

5. App Window at Startup

6. Pop up an Open File Dialog

7. Load File Contents into Text Area

8. from breezypythongui import EasyFrame
import tkinter.filedialog
class FileDialogDemo(EasyFrame):
"""Demonstrates file dialogs and a text area."""
def __init__(self):
"""Sets up the window and widgets."""
EasyFrame.__init__(self, "File Dialog Demo")
self.outputArea = self.addTextArea("", row = 0, column = 0,
columnspan = 2,
width = 80, height = 15)
self.addButton(text = "Open", row = 1, column = 0,
command = self.openFile)
self.addButton(text = "Save As...", row = 1, column = 1,
command = self.saveFileAs)

9. from breezypythongui import EasyFrame
import tkinter.filedialog
class FileDialogDemo(EasyFrame):
"""Demonstrates file dialogs and a text area."""
. . .
# Event handling methods
def openFile(self):
"""Pops up an open file dialog, and if a file is selected,
displays its text in the text area."""
filetypes = [("Python files", "*.py"), ("Text files", "*.txt")]
fileName = tkinter.filedialog.askopenfilename(parent = self,
filetypes = filetypes)
if fileName != "":
file = open(fileName, "r")
text = file.read()
file.close()
self.outputArea.setText(text)
self.setTitle(fileName)
def saveFileAs(self):
"""Pops up a save file dialog, and if a file is selected,
saves the contents of the text area to the file."""
fileName = tkinter.filedialog.asksaveasfilename(parent = self)
text = self.outputArea.getText()
file = open(fileName, "w")
file.write(text)

10. Radio Buttons
Might have different tax rates depending on marital status:
Single – 20%
Married – 15%
Divorced – 10%

11. Radio Buttons
Might have different tax rates depending on marital status:
Single – 20%
Married – 15%
Divorced – 10%

12. Radio Buttons Radio buttons belong to a group
Only one radio button in a group can be selected at any given time
Add a radio button group to a window or panel first, and then add radio buttons to the group

13. Adding a Radio Button Group
The class EasyRadiobuttonGroup is a subclass of tkinter.Frame
The method addRadiobuttonGroup allows spanning over rows and columns in the enclosing container’s grid, as well as an orientation (tkinter.VERTICAL or tkinter.HORIZONTAL)
def addRadiobuttonGroup(self, row, column,
rowspan = 1,
columnspan = 1,
orient = VERTICAL):

14. Adding a Radio Button
The class EasyRadiobuttonGroup is a subclass of tkinter.Frame
The method addRadiobutton requires a text argument and allows a command function whose default does nothing
def addRadiobutton(self, text, command = lambda : 0):

15. Adding a Radio Button # Radio buttons for filing status
self.statusGroup = self.addRadiobuttonGroup(row = 0,
column = 2,
rowspan = 4)
self.single = self.statusGroup.addRadiobutton(text = "Single")
self.married = self.statusGroup.addRadiobutton(text = "Married")
self.divorced = self.statusGroup.addRadiobutton(text = "Divorced")
self.statusGroup["background"] = "pink"
self.single["background"] = "pink"
self.married["background"] = "pink"
self.divorced["background"] = "pink"
self.statusGroup.setSelectedButton(self.single)

16. Accessing a Radio Button
# The event handler method for the button
def computeTax(self):
"""Obtains the data from the input field and uses
them to compute the tax, which is sent to the
output field."""
rate = 0
status = self.statusGroup.getSelectedButton()
if status == self.single:
rate = .20
elif status == self.married:
rate = .15
elif status == self.divorced:
rate = .10
income = self.incomeField.getNumber()
numDependents = self.depField.getNumber()
exemptionAmount =
tax = (income - numDependents * exemptionAmount) * rate
self.taxField.setNumber(max(tax, 0))

17. The value Attribute # The event handler method for the button
def computeTax(self):
"""Obtains the data from the input field and uses
them to compute the tax, which is sent to the
output field."""
rate = 0
status = self.statusGroup.getSelectedButton()["value"]
if status == "Single":
rate = .20
elif status == "Married":
rate = .15
elif status == "Divorced":
rate = .10
income = self.incomeField.getNumber()
numDependents = self.depField.getNumber()
exemptionAmount =
tax = (income - numDependents * exemptionAmount) * rate
self.taxField.setNumber(max(tax, 0))

18. Check Buttons
Multiple check buttons may be selected at the same time

19. Check Buttons # The event handler method for the button
def __init__(self):
"""Sets up the window and widgets."""
EasyFrame.__init__(self, "Check Button Demo",
background = "lightblue")
self.chickCB = self.addCheckbutton(text = "Chicken",
row = 0, column = 0)
self.taterCB = self.addCheckbutton(text = "French fries",
row = 0, column = 1)
self.beanCB = self.addCheckbutton(text = "Green beans",
row = 1, column = 0)
self.sauceCB = self.addCheckbutton(text = "Applesauce",
row = 1, column = 1)

20. Check Buttons def placeOrder(self):
"""Display a message box with the order information."""
message = ""
if self.chickCB.isChecked():
message += "Chicken\n\n"
if self.taterCB.isChecked():
message += "French fries\n\n"
if self.beanCB.isChecked():
message += "Green beans\n\n"
if self.sauceCB.isChecked():
message += "Applesauce\n"
if message == "": message = "No food ordered!"
self.messageBox(title = "Customer Order", message = message)

21. Prompter Boxes
Pops up a dialog for text input; returns the text entered.

22. Prompter Boxes
Pops up a dialog for text input; returns the text entered.

23. Prompter Boxes def getUserName(self):
"""Prompt user for name and display the input in the main window."""
text = self.prompterBox(title = "Input Dialog",
promptString = "Your username:")
self.label["text"] = "Hi, " + text + "!"

24. Working with Colors

25. Working with Colors

26. Use the colorchooser Module
import tkinter.colorchooser .
# Event handling method
def chooseColor(self):
"""Pops up a color chooser and outputs the results."""
colorTuple = tkinter.colorchooser.askcolor()
if not colorTuple[0]: return
((r, g, b), hexString) = colorTuple
self.r.setNumber(int(r))
self.g.setNumber(int(g))
self.b.setNumber(int(b))
self.hex.setText(hexString)
self.canvas["background"] = hexString
askcolor returns the value (None, None) if the user cancels the color chooser dialog

27. What Is a Hex String?
A hex string represents a color as a six-digit hexadecimal number, with the form “#RRGGBB”

28. Programmer-Defined Classes Chapter 9
For Friday
Programmer-Defined Classes
Chapter 9