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![Guide to Programming with Python 26 Creating Buttons (continued) bttn3 = Button(app) bttn3.grid() bttn3["text"] = "Same here!" • Can access widget's options through dictionary-like interface • Key for option is name of the option as a string • Here, set third button's text option to "Same here!” • Useful for changing widget after it has been instantiated (like .config())](https://image.slidesharecdn.com/pythonbasics-240414150707-1557605a/75/Python-is-a-high-level-general-purpose-programming-language-Its-design-philosophy-emphasizes-code-readability-with-the-use-of-significant-indentation-26-2048.jpg)
![Guide to Programming with Python 31 Defining a Method to Create the Widgets def create_widgets(self): self.bttn1 = Button(self, text = "I do nothing!") self.bttn1.grid() self.bttn2 = Button(self) self.bttn2.grid() self.bttn2.configure(text = "Me too!") self.bttn3 = Button(self) self.bttn3.grid() self.bttn3["text"] = "Same here!"](https://image.slidesharecdn.com/pythonbasics-240414150707-1557605a/75/Python-is-a-high-level-general-purpose-programming-language-Its-design-philosophy-emphasizes-code-readability-with-the-use-of-significant-indentation-31-2048.jpg)
![Guide to Programming with Python 36 Binding the Event Handler def create_widget(self): self.bttn = Button(self) self.bttn["text"]= "Total Clicks: 0" self.bttn["command"] = self.update_count self.bttn.grid() • Set widget’s command option to bind activation of widget with event handler • command option bound to update_count() method • When button clicked, update_count() invoked](https://image.slidesharecdn.com/pythonbasics-240414150707-1557605a/75/Python-is-a-high-level-general-purpose-programming-language-Its-design-philosophy-emphasizes-code-readability-with-the-use-of-significant-indentation-36-2048.jpg)
![Guide to Programming with Python 37 Creating the Event Handler def update_count(self): self.bttn_clicks += 1 self.bttn["text"] = "Total Clicks: " + str(self.bttn_clicks) • update_count() increments total number of button clicks and changes text to reflect new total click_counter.py](https://image.slidesharecdn.com/pythonbasics-240414150707-1557605a/75/Python-is-a-high-level-general-purpose-programming-language-Its-design-philosophy-emphasizes-code-readability-with-the-use-of-significant-indentation-37-2048.jpg)
Python is a high-level, general-purpose programming language. Its design philosophy emphasizes code readability with the use of significant indentation
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- 2. Guide to Programmingwith Python 2 Objectives • Work with a GUI toolkit • Create and fill frames • Create and use buttons • Create and use text entries and text boxes • Create and use check buttons • Create and use radio buttons
- 3. Guide to Programmingwith Python 3 The Mad Lib Program Figure 10.1: Sample run of the Mad Lib program A nicely laid-out GUI awaits the user’s creativity.
- 4. Guide to Programmingwith Python 4 The Mad Lib Program (continued) Figure 10.2: Sample run of the Mad Lib program The user has entered all of the necessary information.
- 5. Guide to Programmingwith Python 5 The Mad Lib Program (continued) Figure 10.3: Sample run of the Mad Lib program After clicking Click for story button, text box displays masterpiece.
- 6. Guide to Programmingwith Python 6 Examining A GUI Figure 10.4: Examining a GUI You’ll learn to create all of these GUI elements.
- 7. Guide to Programmingwith Python 7 Examining A GUI (continued) Table 10.1: Selected GUI Elements
- 8. Guide to Programmingwith Python 8 Understanding Event-Driven Programming • Event-driven program: A program that responds to actions regardless of the order in which they occur • Event: Something that happens involving a program's objects • Event handler: Code that runs when a specific event occurs • Bind: To associate an event with an event handler • Event loop: A loop that checks for events and calls appropriate event handlers when they occur
- 9. Guide to Programmingwith Python 9 Understanding Event-Driven Programming (continued) • GUI programs traditionally event-driven • Mad Lib without event-driven programming – Ask series of questions with raw_input() function – Ask for name of a person, plural noun... – User must provide each piece of information, in order • Mad Lib with event-driven programming – Can use a GUI – User can enter the information in any order
- 10. Guide to Programmingwith Python 10 Using A Root Window • Root Window – Foundation of GUI program – Foundation upon which to add all other GUI elements – Like root of tree, anchors all other parts
- 11. Guide to Programmingwith Python 11 The Simple GUI Program Figure 10.5: Sample run of the Simple GUI program The program creates only a lone window. simple_gui.py
- 12. Guide to Programmingwith Python 12 The Simple GUI Program (continued) • GUI programs can generate console window too • Console window helpful to see error messages • On Windows machine can suppress console window by changing program extension from py to pyw
- 13. Guide to Programmingwith Python 13 Importing the Tkinter Module from Tkinter import * • Tkinter is a GUI module • Imports all Tkinter into global scope • Normally, avoid this kind of import • Some modules designed to be imported this way • Saves typing and makes for cleaner code
- 14. Guide to Programmingwith Python 14 Creating a Root Window root = Tk() • To create a root window, instantiate object of the Tkinter class Tk • Because of from Tkinter import *, no need to prefix the module name
- 15. Guide to Programmingwith Python 15 Modifying a Root Window root.title("Simple GUI") root.geometry("200x100") • title() – Sets title of root window – Takes string • geometry() – Sets size of the root window – Takes string (not integers) for window’s width and height, separated by the "x" character
- 16. Guide to Programmingwith Python 16 Entering a Root Window’s Event Loop root.mainloop() • Root window's event loop entered • Window stays open, waiting to handle events
- 17. Guide to Programmingwith Python 17 Using Labels • Widget: GUI elements (short for "window gadget") • Label widget – Uneditable text or icons (or both) – Often used to label other widgets – Unlike most other widgets, labels aren’t interactive
- 18. Guide to Programmingwith Python 18 The Labeler Program Figure 10.7: Sample run of the Labeler program A label can provide information about a GUI. labeler.py
- 19. Guide to Programmingwith Python 19 Creating a Frame app = Frame(root) • Master: A widget that contains other widgets • Layout Manager: Controls arrangement of widgets • Frame is widget that can hold other widgets • When creating widget, must pass its master to constructor of new object • Here, root is master that contains app
- 20. Guide to Programmingwith Python 20 Creating a Frame (continued) app.grid() • grid() – Method that all widgets have – Associated with grid layout manager – Can be used to create desired layout of widgets
- 21. Guide to Programmingwith Python 21 Creating a Label lbl = Label(app, text = "I'm a label!") lbl.grid() • Label Class – For a label widget – Master is first argument passed to constructor – text parameter for widget's text – grid() method invoked ensures widget visible (places widget at a default location in frame if called with no arguments)
- 22. Guide to Programmingwith Python 22 Using Buttons • Button widget – Is a button in GUI – Can be activated by user to perform some action
- 23. Guide to Programmingwith Python 23 The Lazy Buttons Program Figure 10.8: Sample run of the Lazy Buttons program You can click these lazy buttons all you want; they won’t do a thing. lazy_buttons.py
- 24. Guide to Programmingwith Python 24 Creating Buttons bttn1 = Button(app, text = "I do nothing!") bttn1.grid() • Button Class – For a button widget – Master is first argument passed to constructor – text parameter for widget's text – grid() method invoked ensures widget visible
- 25. Guide to Programmingwith Python 25 Creating Buttons (continued) bttn2 = Button(app) bttn2.grid() bttn2.configure(text = "Me too!") • Can add blank button to the frame • configure() method sets or changes widget options – Useful for changing widget after it has been instantiated
- 26. Guide to Programmingwith Python 26 Creating Buttons (continued) bttn3 = Button(app) bttn3.grid() bttn3["text"] = "Same here!" • Can access widget's options through dictionary-like interface • Key for option is name of the option as a string • Here, set third button's text option to "Same here!” • Useful for changing widget after it has been instantiated (like .config())
- 27. Guide to Programmingwith Python 27 Creating a GUI Using a Class • Organizing code into classes can make programming easier • Often beneficial to write larger GUI programs in OOP style
- 28. Guide to Programmingwith Python 28 The Lazy Buttons 2 Program Figure 10.9: Sample run of the Lazy Buttons 2 program Program appears the same but significant changes under the hood.
- 29. Guide to Programmingwith Python 29 Defining the Application Class class Application(Frame): """ A GUI application with three buttons. """ def __init__(self, master): • Instead of instantiating Frame object, will instantiate Application object • Application object becomes just a specialized type of Frame object • master will be the Tk window that the frame belongs to (root in all our examples so far)
- 30. Guide to Programmingwith Python 30 Defining a Constructor Method def __init__(self, master): Frame.__init__(self, master) self.grid() self.create_widgets() • Frame constructor called first – This is what is used instead of super() for old object classes • Pass Application object’s master, so it gets properly set as master • Invoke Application object’s create_widgets() method
- 31. Guide to Programmingwith Python 31 Defining a Method to Create the Widgets def create_widgets(self): self.bttn1 = Button(self, text = "I do nothing!") self.bttn1.grid() self.bttn2 = Button(self) self.bttn2.grid() self.bttn2.configure(text = "Me too!") self.bttn3 = Button(self) self.bttn3.grid() self.bttn3["text"] = "Same here!"
- 32. Guide to Programmingwith Python 32 Creating the Application Object # main root = Tk() root.title("Lazy Buttons 2") root.geometry("200x85") app = Application(root) root.mainloop() • Application object created here, not Frame object • root is still master of object • root.mainloop() still invoked lazy_buttons2.py
- 33. Guide to Programmingwith Python 33 Binding Widgets and Event Handlers • So far, GUI programs haven't had event handlers • Widgets are like light fixtures without electrical wiring • Write event handlers and bind them with events
- 34. Guide to Programmingwith Python 34 The Click Counter Program Figure 10.10: Sample run of the Click Counter program Button’s event handler updates number of times button clicked.
- 35. Guide to Programmingwith Python 35 Setting Up the Program from Tkinter import * class Application(Frame): def __init__(self, master): Frame.__init__(self, master) self.grid() self.bttn_clicks = 0 # number clicks self.create_widget()
- 36. Guide to Programmingwith Python 36 Binding the Event Handler def create_widget(self): self.bttn = Button(self) self.bttn["text"]= "Total Clicks: 0" self.bttn["command"] = self.update_count self.bttn.grid() • Set widget’s command option to bind activation of widget with event handler • command option bound to update_count() method • When button clicked, update_count() invoked
- 37. Guide to Programmingwith Python 37 Creating the Event Handler def update_count(self): self.bttn_clicks += 1 self.bttn["text"] = "Total Clicks: " + str(self.bttn_clicks) • update_count() increments total number of button clicks and changes text to reflect new total click_counter.py
- 38. Guide to Programmingwith Python 38 Using Text and Entry Widgets and the Grid Layout Manager • Entry widget is good for single line of text • Text widget is great for multi-line blocks of text • Can read contents of either • Can insert text into either • Grid layout manager lets you place widgets at specific locations by treating frame as a grid
- 39. Guide to Programmingwith Python 39 The Longevity Program Figure 10.11: Sample run of the Longevity Program With incorrect password, program politely refuses to divulge its secret.
- 40. Guide to Programmingwith Python 40 The Longevity Program (continued) Figure 10.12: Sample run of the Longevity Program With correct password, program shares its knowledge to long life.
- 41. Guide to Programmingwith Python 41 Placing a Widget with the Grid Layout Manager Figure 10.13: Illustrates placement of button widgets Frame can be seen as a grid of cells at row and column numbers.
- 42. Guide to Programmingwith Python 42 Placing a Widget with the Grid Layout Manager def create_widgets(self): self.inst_lbl = Label(self, text = "Enter password for the secret of longevity") self.inst_lbl.grid(row = 0, column = 0, columnspan = 2, sticky = W) • grid() method – row takes integer; defines the row in which the object is placed (within the widget’s master) – column takes integer; defines the column in which the object is placed (within the widget’s master) – columnspan takes integer; defines width in columns – sticky takes constants (N, S, E, W); positions widget at specified edge of cell (centered by default)
- 43. Guide to Programmingwith Python 43 Placing a Widget with the Grid Layout Manager # create label for password self.pw_lbl = Label(self, text = "Password: ") self.pw_lbl.grid(row = 1, column = 0, sticky = W) • Creates a label that appears in row 1, left-justified
- 44. Guide to Programmingwith Python 44 Creating an Entry Widget # create entry widget to accept password self.pw_ent = Entry(self) self.pw_ent.grid(row = 1, column = 1, sticky = W) • Entry widget accepts and displays line of text
- 45. Guide to Programmingwith Python 45 Creating a Button Widget # create submit button self.submit_bttn = Button(self, text = "Submit", command = self.reveal) self.submit_bttn.grid(row = 2, column = 0, sticky = W) • Bind the activation of button with reveal() method • Place button in next row, left-justified
- 46. Guide to Programmingwith Python 46 Creating a Text Widget # create text widget to display message self.secret_txt = Text(self, width = 35, height = 5, wrap = WORD) self.secret_txt.grid(row = 3, column = 0, columnspan = 2, sticky = W) • wrap parameter determines how text in the box is wrapped – WORD wraps entire words – CHAR wraps characters – NONE no wrapping (can only write text on the first line)
- 47. Guide to Programmingwith Python 47 Getting and Inserting Text with Text- Based Widgets def reveal(self): """ Display message based on password. """ contents = self.pw_ent.get() if contents == "secret": message = "Here's the secret..." else: message = "That's not the correct..." self.secret_txt.delete(0.0, END) self.secret_txt.insert(0.0, message)
- 48. Guide to Programmingwith Python 48 Getting and Inserting Text with Text- Based Widgets (continued) • get() returns text from text-based widget • delete() deletes text from text-based widget – Can take single index or beginning and ending point – Pass floating-point number for row and column – Tkinter provides constants, such as END • insert() inserts a string into a text-based widget – Takes an insertion position and a string – Pass floating-point number for row and column longevity.py
- 49. Guide to Programmingwith Python 49 Using Check Buttons • Check buttons allow user to select any number of choices from a group • Provides flexibility for user and control of limiting choices for programmer
- 50. Guide to Programmingwith Python 50 The Movie Chooser Program Figure 10.14: Sample run of the Movie Chooser program The results of the user’s selections show up in the text box.
- 51. Guide to Programmingwith Python 51 Allowing a Widget’s Master to Be Its Only Reference def create_widgets(self): Label(self, text = "Choose your favorite movie types" ).grid(row = 0, column = 0, sticky = W) • Label object – Not assigned to variable – Can't be directly accessed – Connected to the program by its master
- 52. Guide to Programmingwith Python 52 Creating Check Buttons # create Comedy check button self.likes_comedy = BooleanVar() • BooleanVar – Special class from Tkinter module – Can reflect check button’s status – Required by Checkbutton object
- 53. Guide to Programmingwith Python 53 Creating Check Buttons (continued) Checkbutton(self, text = "Comedy", variable = self.likes_comedy, command = self.update_text ).grid(row = 2, column = 0, sticky = W) • variable takes BooleanVar for status of check button • command takes function or method to call when check button is checked or unchecked
- 54. Guide to Programmingwith Python 54 Getting the Status of a Check Button def update_text(self): likes = "" if self.likes_comedy.get(): likes += "You like comedic movies.n" • BooleanVar – Can’t access the value directly – Must invoke object’s get() method movie_chooser.py
- 55. Guide to Programmingwith Python 55 Using Radio Buttons • Radio buttons allow user to select one from a group of choices • Provides programmer control by limiting range of choices and allowing only single choice
- 56. Guide to Programmingwith Python 56 The Movie Chooser 2 Program Figure 10.15: Sample run of the Movie Chooser program The user can select only a single movie type.
- 57. Guide to Programmingwith Python 57 Creating Radio Buttons # create variable for single, favorite type self.favorite = StringVar() • StringVar – Special class from Tkinter module – Can reflect status of a group of radio buttons – Required by Radiobutton objects
- 58. Guide to Programmingwith Python 58 Creating Radio Buttons (continued) Radiobutton(self, text = "Comedy", variable = self.favorite, value = "comedy.", command = self.update_text ).grid(row = 2, column = 0, sticky = W) • variable parameter gets StringVar self.favorite • When radio button is selected, StringVar assigned string referenced by object’s value option • When Comedy radio button selected, StringVar self.favorite assigned "comedy."
- 59. Guide to Programmingwith Python 59 Getting a Value from a Group of Radio Buttons message = "Your favorite type of movie is " message += self.favorite.get() • get() method returns string referenced by the StringVar that all Radiobutton objects share • When Comedy radio button selected, self.favorite.get() returns "comedy " movie_chooser2.py
- 60. Guide to Programmingwith Python 60 The Mad Lib Program mad_lib.py
- 61. Guide to Programmingwith Python 61 Summary • A GUI is a graphical user interface • A widget, short for window gadget, is a GUI element • A master widget contains other widgets • A layout manager controls the arrangement of widgets • An event-driven program responds to actions regardless of the order in which they occur • An event is something that happens involving a program’s objects
- 62. Guide to Programmingwith Python 62 Summary (continued) • An event handler is code that runs when a specific event occurs • To bind is to associate an event with an event handler • An event loop checks for events and, based on them, calls the appropriate event handlers • Tkinter is a GUI module • A Label object represents a label widget • A Frame object represents a frame widget
- 63. Guide to Programmingwith Python 63 Summary (continued) • A Button object represents a button widget • An Entry object represents a text entry widget • A Text object represents a text box widget • A Checkbutton object represents a check button widget • A Radiobutton object represents a radio button widget