Python Tkinter scrollbar for frame
Question: My objective is to add a vertical scroll bar to a frame which has several
labels in it. The scroll bar should automatically enabled as soon as the
labels inside the frame exceed the height of the frame. After searching
through, I found [this](http://stackoverflow.com/questions/3085696/adding-a-
scrollbar-to-a-grid-of-widgets-in-tkinter) useful post. Based on that post I
understand that in order to achieve what i want, (correct me if I am wrong, I
am a beginner) I have to create a Frame first, then create a Canvas inside
that frame and stick the scroll bar to that frame as well. After that, create
another frame and put it inside the canvas as a window object. So, i finally
come up with this

    
    
    from Tkinter import *
    
    def data():
        for i in range(50):
           Label(frame,text=i).grid(row=i,column=0)
           Label(frame,text="my text"+str(i)).grid(row=i,column=1)
           Label(frame,text="..........").grid(row=i,column=2)
    
    def myfunction(event):
        canvas.configure(scrollregion=canvas.bbox("all"),width=200,height=200)
    
    root=Tk()
    sizex = 800
    sizey = 600
    posx  = 100
    posy  = 100
    root.wm_geometry("%dx%d+%d+%d" % (sizex, sizey, posx, posy))
    
    myframe=Frame(root,relief=GROOVE,width=50,height=100,bd=1)
    myframe.place(x=10,y=10)
    
    canvas=Canvas(myframe)
    frame=Frame(canvas)
    myscrollbar=Scrollbar(myframe,orient="vertical",command=canvas.yview)
    canvas.configure(yscrollcommand=myscrollbar.set)
    
    myscrollbar.pack(side="right",fill="y")
    canvas.pack(side="left")
    canvas.create_window((0,0),window=frame,anchor='nw')
    frame.bind("<Configure>",myfunction)
    data()
    root.mainloop()
    

  1. Am I doing it right? Is there better/smarter way to achieve the output this code gave me?
  2. Why must I use grid method? (I tried place method, but none of the labels appear on the canvas.)
  3. What so special about using anchor='nw' when creating window on canvas?

Please keep your answer simple as I am a beginner. Thanks for your help.


Answer: Here is an example:

    
    
    from Tkinter import *   # from x import * is bad practice
    from ttk import *
    
    # http://tkinter.unpythonic.net/wiki/VerticalScrolledFrame
    
    class VerticalScrolledFrame(Frame):
        """A pure Tkinter scrollable frame that actually works!
        * Use the 'interior' attribute to place widgets inside the scrollable frame
        * Construct and pack/place/grid normally
        * This frame only allows vertical scrolling
    
        """
        def __init__(self, parent, *args, **kw):
            Frame.__init__(self, parent, *args, **kw)            
    
            # create a canvas object and a vertical scrollbar for scrolling it
            vscrollbar = Scrollbar(self, orient=VERTICAL)
            vscrollbar.pack(fill=Y, side=RIGHT, expand=FALSE)
            canvas = Canvas(self, bd=0, highlightthickness=0,
                            yscrollcommand=vscrollbar.set)
            canvas.pack(side=LEFT, fill=BOTH, expand=TRUE)
            vscrollbar.config(command=canvas.yview)
    
            # reset the view
            canvas.xview_moveto(0)
            canvas.yview_moveto(0)
    
            # create a frame inside the canvas which will be scrolled with it
            self.interior = interior = Frame(canvas)
            interior_id = canvas.create_window(0, 0, window=interior,
                                               anchor=NW)
    
            # track changes to the canvas and frame width and sync them,
            # also updating the scrollbar
            def _configure_interior(event):
                # update the scrollbars to match the size of the inner frame
                size = (interior.winfo_reqwidth(), interior.winfo_reqheight())
                canvas.config(scrollregion="0 0 %s %s" % size)
                if interior.winfo_reqwidth() != canvas.winfo_width():
                    # update the canvas's width to fit the inner frame
                    canvas.config(width=interior.winfo_reqwidth())
            interior.bind('<Configure>', _configure_interior)
    
            def _configure_canvas(event):
                if interior.winfo_reqwidth() != canvas.winfo_width():
                    # update the inner frame's width to fill the canvas
                    canvas.itemconfigure(interior_id, width=canvas.winfo_width())
            canvas.bind('<Configure>', _configure_canvas)
    
    
    if __name__ == "__main__":
    
        class SampleApp(Tk):
            def __init__(self, *args, **kwargs):
                root = Tk.__init__(self, *args, **kwargs)
    
    
                self.frame = VerticalScrolledFrame(root)
                self.frame.pack()
                self.label = Label(text="Shrink the window to activate the scrollbar.")
                self.label.pack()
                buttons = []
                for i in range(10):
                    buttons.append(Button(self.frame.interior, text="Button " + str(i)))
                    buttons[-1].pack()
    
        app = SampleApp()
        app.mainloop()
    

It does not yet have the mouse wheel bound to the scrollbar but it is
possible. Scrolling with the wheel can get a bit bumpy, though.

edit:

to 1)  
IMHO scrolling frames is somewhat tricky in Tkinter and does not seem to be
done a lot. It seems there is no elegant way to do it.  
One problem with your code is that you have to set the canvas size manually -
that's what the example code I posted solves.

to 2)  
You are talking about the data function? Place works for me, too. (In general
I prefer grid).

to 3)  
Well, it positions the window on the canvas.

One thing I noticed is that your example handles mouse wheel scrolling by
default while the one I posted does not. Will have to look at that some time.

