This Week GUIs

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This Week -- GUIs

• Graphical User Interfaces
• windows
• widgets
• containers
• events
• Tkinter (Tool kit interface)
• Tk is a common GUI toolkit
• Tkinter is the python module that interfaces with
  Tk

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What is a GUI?

• A window consists of
• containers
• Frames
• widgets
• Buttons
• Entry (text fields)
• Menus
• Labels

Window
Labels
Buttons
Frame (all but title bar)
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Basic GUI Programming Steps

• How do you want the GUI to look?
• What do you want the GUI to do?
• Bind 1. and 2. together.
• Write code to wait for user input.

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How do you want the GUI to look?

• Import Tkinter
• from Tkinter import
• Create a window
• window Tk()
• Pack a container into it
• container1 Frame(window)
• container1.pack()
• Pack widgets into the container
• button1 Button(container1, textEnter)
• button1.pack()
• button2 Button(container1, textQuit)
• button2.pack()

Pack puts the container into the window and makes
it visible.
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What do you want the GUI to do?

• React to user events
• Button clicks
• Text Entry
• Checkbox Selections
• Menu Selections
• Write event handlers (functions) to react to
  the user input.
• Example Enter Button
• def enter()
• print hello

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Binding What with How

• Example Enter Button
• def enter()
• print hello
• button1 Button(container1, textEnter)
• Need to bind button1 with the function enter().
• button1 Button(container1, textEnter, \
  commandenter)
• Note The command feature does not allow
  arguments.

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Using Functions With Arguments

• Example Quit Button
• def quit(w)
• w.destroy()
• button2 Button(container1, textQuit,\
  command??)
• Use a python keyword lambda
• button_quit lambdaquit(window)
• button2 Button(container1, textQuit,\
• commandbutton_quit)

close the window w
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More on Lambda

• Example
• gtgtgt def f(x,y)
• gtgtgt return xy
• gtgtgt create a function variable g() to
• gtgtgt represent the function f(x,y)
• gtgtgt g lambda f(a,b)
• gtgtgt define a and b to use g()
• gtgtgt a 10
• gtgtgt b 5
• gtgtgt g()
• 15

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Another Example

• Want to add a Label to our container.
• welcome Label(container1,\
• textWelcome to my window.)
• welcome.pack()
• Lets add another Label and a (text) Entry.
• name Label(container1, \
• textWhat is your name?)
• name.pack()
• name_entry Entry(container1)
• name_entry.pack()

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Example Continued

• Want to be able to change the text in
• welcome Label(container1, \
• textWelcome to my window.)
• Make the text a variable!
• message StringVar()
• message.set("Welcome to my window.")
• welcome Label(frame, textvariablemessage)

When we click Enter wed like to see
textvariable means the text can be altered --
only use with a variable.
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Putting it all together

• def enter(var, input)
• var.set(Welcome input.get())
• message StringVar()
• message.set("Welcome to my window.")
• welcome Label(frame, textvariablemessage)
• welcome.pack()
• name Label(container1, textWhat is your
  name?)
• name.pack()
• name_entry Entry(container1)
• name_entry.pack()
• button_enter lambdaenter(message, name_entry)
• button1 Button(container1, textEnter, \
• commandbutton_enter)
• button1.pack()

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Opening our Window

• We run the window and transfer control to the
  user by typing
• window.mainloop()
• at the end.

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Tkinter Mutable Type Variables

• Immutable types in Python (cant be changed)
• string long bool int
• Tkinter mutable equivalent types (can be
  changed)
• StringVar() DoubleVar() BooleanVar() IntVar()
• Example
• mynum IntVar()
• mynum.get()
• mynum.set(10)

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This Week

• Checkbuttons
• Dropdown menus
• grid vs. pack
• Simple Notepad implementation

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Checkbuttons