Tkinter Lesson 5 Notes: A Wealth of Widgets

• Making "child" windows
  • A root GUI window can launch "child" windows using Toplevel()
    • root = Tk()
    • win2 = Toplevel(root)
  • Toplevel() requires the name of the associated root window.
  • When the root window is destroyed, all associated Toplevel() windows will also be destroyed.
• Window Methods
  • win2.title("title text")
       Adds title to top of window
  • win2.transient(root_window)
       Makes window so it can close, but not minimize or resize.
  • win2.resizable(width=YES, height=NO)
       Sets whether or not the window can be resized.
  • win2.maxsize(width=#, height=#)
       Sets the maximum size of the window.
  • win2.minsize(width=#, height=#)
       Sets the minimum size of the window.
• Toplevel() Example
  from Tkinter import *
  root = Tk()
  root.title("Toplevels")
  root.maxsize(width=300, height=200)
  root.minsize(width=150, height=100)
  root.resizable(width=YES, height=NO)
  
  def child1():
      c1 = Toplevel(root)
      c1.title("Child One")
      c1.transient(root)
      Label(c1, text="This window is set as transient.").grid()
  
  def child2():
      c2 = Toplevel(root)
      c2.title("Child Two")
      Label(c2, text="This is a regular toplevel window.").grid()
  
  Label(root, text="Toplevel Practice").grid(row=0, column=0, columnspan=2)
  Button(root, text="Child 1", command = child1).grid(row=1, column=0)
  Button(root, text="Child 2", command = child2).grid(row=1, column=1)
  
• Control Variables
  • Control Variables are variables that can hold values for GUI widgets to access and update as needed
  • There are two types of control variables:
    • IntVar() -- holds integers
    • StringVar() -- hold string values
  • Set the value of a control variable using set()
    var = IntVar()
var.set(1)
  • Get the value out of a control variable using get()
    number = var.get()
  • To use control variables:
    • Assign the control variable class to a name
         num_holder = IntVar()
    • Set widget to use that variable
         rb1 = Radiobutton(root, text = "Five", variable = num_holder, value=5, command = num_holder.set(value))
• Radiobutton()
  • A Radiobutton() is a widget that allows the user to choose one out of a list of options.
  • The Radiobutton() widget consists of a select button and text. You do not have to create a separate Label() for the radiobutton.
  • Radiobuttons are designed so that each button passes a unique "value" to a common "variable". Other portions of the program can then see what the value of this variable is and act accordingly.
  • To link the radiobuttons together, they must each be set to the same variable, and the variable must be a special "control variable"
  • Example:
   rb1 = Radiobutton(root, text = "First Choice", variable = num, value = 1)
   rb2 = Radiobutton(root, text="Second choice", variable = num, value=2)
• Example Radiobuttons()
  from Tkinter import *
  root = Tk()
  
  lbl = Label(root, text="Pre-click", bg="#ffffcc")
  lbl.grid(sticky="EW")
  
  foo = IntVar()
  def text_update():
      number = foo.get()
     lbl.configure(text = number)
  
  rb1 = Radiobutton(root, text = "First Choice", variable=foo, value=1, command = text_update)
  rb1.grid()
  
  rb2 = Radiobutton(root, text = "Second Choice", variable=foo, value=2, command = text_update)
  rb2.grid()
  
  rb3 = Radiobutton(root, text = "Third Choice", variable=foo, value=3, command = text_update)
  rb3.grid()
  
  
• Checkbutton()
  • Checkboxes provide non-exclusive choices (the user can pick more than one).
  • Checkboxes are usually linked to a control variable, and provide both an "onvalue" and an "offvalue"
• Checkbox Example
  from Tkinter import *
  root = Tk()
  
  x1 = StringVar()
  name1 = Checkbutton(root, text = "Pizza", variable = x1, onvalue="Pizza\n", offvalue="")
  name1.grid()
  
  x2 = StringVar()
  name2 = Checkbutton(root, text="Salad", variable = x2, onvalue="Salad\n", offvalue="")
  name2.grid()
  
  x3 = StringVar()
  name3 = Checkbutton(root, text="Soda", variable = x3, onvalue = "Soda\n", offvalue="")
  name3.grid()
  
  x4 = StringVar()
  name4 = Checkbutton(root, text="Dessert", variable = x4, onvalue="Dessert\n", offvalue="")
  name4.grid()
  
  def ourmenu():
      menu = x1.get() + x2.get() + x3.get() + x4.get()
      lbl.configure(text = menu)
  
  btn = Button(root, text="Place Order", command = ourmenu)
  btn.grid()
  
  lbl = Label(root, text = "", bg = "red", fg="white")
  lbl.grid(sticky=EW)
  
• Listbox()
  • Creates a box with choices for the user to select.
  • Options include:
    • selectmode = SINGLE
      Determines how items in list may be selected. Choices are SINGLE, MULTIPLE, BROWSE, or EXTENDED
    • xscrollcommand OR yscrollcommand
      Links the list box to a scroll bar.
    • height = # , width = #
      Sets the height or width of the listbox.
• Listbox() Methods
  • listbox.activate(index)
    Selects the item in the listbox at the given index
  • listbox.curselection()
    Returns the numerical indices for the currently selected choices
  • listbox.delete(index)
    Deletes the choice at the given index
  • listbox.index(index)
    Adjusts the listbox so that the choice at the given index is displayed in the top of the window
  • listbox.insert(index, choice)
    Adds choices to the listbox. Index may be a numerical value or the keyword END
  • listbox.selection_clear(index)
    Deselects the choice at the given index
  • listbox.selection_includes(index)
    Returns TRUE if the choice at the given index is currently selected
  • listbox.selection(index)
    Selects the choice at the given index.
• Listbox() Example
  from Tkinter import *
  root = Tk()
  root.title("Listbox")
  
  lbl = Label(root, text = "", bg="white", fg="midnightblue", font = ("arial", 16))
  lbl.grid()
  
  choices = ["Red", "Orange", "Yellow", "Green", "Blue", "Purple"]
  list = Listbox(root, height=6, selectmode = MULTIPLE)
  list.grid()
  for item in choices:
      list.insert(END, item)
  
  def view_selected():
      x = list.curselection()
      lbl.configure(text = x)
  
  btn = Button(root, text = "Click for values", command = view_selected)
  btn.grid()
  
• Scrollbar()
  • A Scrollbar() is a widget that allows the information in another widget to be scrolled.
  • Scrollbars must be bound to scrollable widgets, such as Listbox(), Text(), and Canvas()
  • Scrollbars may be horizontal (xview), vertical (yview) or both.
  • To bind a scrollbar to a scrollable widget, use the command = "" option in the scrollbar, then set the command to widget.xview.
    Example:
    listbox = Listbox(root)
scroll = Scrollbar(root, command = listbox.xview)
listbox.configure(xscrollcommand = scroll.set)
• Scrollbar Options
  • troughcolor = "color_name"
    Sets color of the slider trough
  • orient = VERTICAL
    Sets orientation of the scrollbar. Options are VERTICAL and HORIZONTAL.
• Scrollbar() Example
  from Tkinter import *
  root = Tk()
  root.title("Listbox")
  
  lbl = Label(root, text = "", bg="white", fg="midnightblue", font = ("arial", 16))
  lbl.grid(row = 0, column = 0, columnspan = 2)
  
  choices = ["Red", "Orange", "Yellow", "Green", "Blue", "Purple", "Orchid", "Beige"]
  list = Listbox(root, height=4, selectmode = MULTIPLE)
  for item in choices:
      list.insert(END, item)
  
  scroll = Scrollbar(root, command = list.yview)
  list.configure(yscrollcommand = scroll.set)
  list.grid(row = 1, column = 0, sticky = NS)
  scroll.grid(row = 1, colum = 1, sticky = NS)
  
  def view_selected():
      x = list.curselection()
      lbl.configure(text = x)
  
  btn = Button(root, text = "Click for values", command = view_selected)
  btn.grid(row = 2, column = 0, columnspan = 2)
• Scale()
  • Scale() creates a sliding scale widget for selecting numbers
  • Methods for scale:
    • scale.get()
      Retrieves the current value of the scale
    • scale.set()
      Sets the slider at a certain value on the scale
• Options for Scale()
  • tickinterval = # Determines which guide numbers are displayed on scale
  • from_ = #
    Lowest number for scale
  • to = #
    Highest number for scale
  • orient = VERTICAL
    Whether scale should be HORIZONTAL or VERTICAL
  • resolution = #
    Numerical distance between each value on the scale
  • showvalue = TRUE
    Whether of not to display which number is currently selected
  • troughcolor = "colorname"
    What color should the slider trough be
• Scale() Example
  from Tkinter import *
  root = Tk()
  root.title("Scale")
  
  lbl = Label(root, text = "", bg = "white", \
     fg = "seagreen", font=("arial", 16, "bold") )
  lbl.grid()
  
  def getnum(event):
      x = scale.get()
      lbl.configure(text = x)
  
  scale = Scale(root, orient=HORIZONTAL, length = 100, \
      from_=0, to=100, tickinterval=50, \
     command = getnum)
  scale.set(0)
  scale.grid()
  
• Message()
  • The Message() widget is a quick way to display multi-line text.
  • In Message, the text = "" portion can span more than one line.
  • Example:
    msg = Message(root, text = "Here is line one"
"Here is line two"
"Here is line three"
"That's the end of my message text")
    
• Message Example:
  from Tkinter import *
  root = Tk()
  
  def message():
      rt2 = Toplevel(root)
      msg = Message(rt2, text="Here is the first line of text. "
          "Here is the next line of text. "
          "Now we are on line three. "
          "Oooh, look mom, line four! "
          "Okay, that's enough. Goodbye.", bg="white", fg="red")
      msg.grid()
      rt2.transient(root)
  
  Button(root, text = "Message", command = message).grid()