unsettling tkinter bug -- or is it just me?

[Robert Roy]

On Mon, 12 Jun 2000 18:14:36 -0700, Bob Lewis <bobl at tricity.wsu.edu>
wrote:

>Consider the following code:
>--------
>
>from Tkinter import *
>
>root = Tk()
>img = PhotoImage(file='bobl.gif')
>
>def func():
>    cnvs = Canvas(root, width=img.width(), height=img.height())
>    cnvs.create_image(0,0, image=img, anchor=NW)
>    cnvs.pack(side=TOP)
>    Button(root, text='Quit', command=root.quit).pack()
>
>func()
>root.mainloop()
>--------
>This runs just fine: It creates a root toplevel with "bobl.gif" displayed
>in it and a "Quit" button.
>
>Now we make one wafer-thin change: Move the the "img =" inside "func()":
>--------
>from Tkinter import *
>
>root = Tk()
>
>def func():
>    img = PhotoImage(file='bobl.gif')
>    cnvs = Canvas(root, width=img.width(), height=img.height())
>    cnvs.create_image(0,0, image=img, anchor=NW)
>    cnvs.pack(side=TOP)
>    Button(root, text='Quit', command=root.quit).pack()
>
>func()
>root.mainloop()
>--------
>And now, while the canvas has the right dimensions, the image does
>not appear.  Okay, so "img" went from a global to local scope, but
>that shouldn't have affected execution, right?  Have I missed something?
>
>This is on a Red Hat Linux system running versions 1.5.2-13 of both
>python and tkinter.
>
>	- Bob Lewis
>	  bobl at tricity.wsu.edu

I was bitten by this also. You must persist the PhotoImage instance
independently. I seem to recall that this is documented somewhere, but
I can't remember where.


Bob