Environment: Windows 10, Python 3.9.5
If I try to display a prompt (using tkinter.messagebox functions) before creating the root window, I cannot assign a window icon to the root window. The iconphoto call fails with the error, even though the icon given is a valid PhotoImage object:
_tkinter.TclError: can't use "pyimage1" as iconphoto: not a photo image
In this instance, my objective is to display a prompt to the user before the program starts, or even potentially ask a question (with tkinter.messagebox.askyesno) that may affect the operation of the GUI.
For example, the following code will cause this error:
## this is a base64 GIF to use as a window icon
icon_window_b64 = 'R0lGODlhIAAgAKECAP8AAP///wAAAAAAACH5BAEKAAIALAAAAAAgACAAAAJrlI+gy4oPX5sgWkFzu0f7en0iCI1faY5JKq5TEGRw5jLw3NzxZMj6rvgBR8LijQUwCpFBJY6ZVEIXzmnTaI1ip84nq3v8gsOmJfVHw7zIZ++iZhvG073spmNnoLKWPGfKUccUKHFCGNFyUQAAOw=='
## import tkinter
import tkinter
## import the messagebox module so we can make the prompt
import tkinter.messagebox
## show the prompt
tkinter.messagebox.showinfo('A prompt', 'Dismiss this for an exception')
## create the root window
root = tkinter.Tk()
## set the size of the root window
root.geometry('200x20')
## create the photoimage object from the base64 GIF
icon_window = tkinter.PhotoImage(data = icon_window_b64)
## put a label in to the window
tkinter.Label(root, text='This is a test').pack()
## set the window icon for the root window
root.iconphoto(False, icon_window)
## let the GUI block forevermore
root.mainloop()
However, this code will not:
## this is a base64 GIF to use as a window icon
icon_window_b64 = 'R0lGODlhIAAgAKECAP8AAP///wAAAAAAACH5BAEKAAIALAAAAAAgACAAAAJrlI+gy4oPX5sgWkFzu0f7en0iCI1faY5JKq5TEGRw5jLw3NzxZMj6rvgBR8LijQUwCpFBJY6ZVEIXzmnTaI1ip84nq3v8gsOmJfVHw7zIZ++iZhvG073spmNnoLKWPGfKUccUKHFCGNFyUQAAOw=='
## import tkinter
import tkinter
## import the messagebox module so we can make the prompt
import tkinter.messagebox
## create the root window
root = tkinter.Tk()
## show the prompt
tkinter.messagebox.showinfo('A prompt', 'No exceptions here!')
## set the size of the root window
root.geometry('200x20')
## create the photoimage object from the base64 GIF
icon_window = tkinter.PhotoImage(data = icon_window_b64)
## put a label in to the window
tkinter.Label(root, text='This is a test').pack()
## set the window icon for the root window
root.iconphoto(False, icon_window)
## let the GUI block forevermore
root.mainloop()
The key difference in the second code block is that the prompt is created after the tkinter.Tk() object. Obviously, I have few workarounds I can use:
- Not use a window icon.
- withdraw() the root immediately after creation so that it is not seen, and show it again after the call to the prompt so that it appears that the prompt came first.
- Don't use the prompt functions at all (tkinter.messagebox, tkinter.dialog, etc), and question the user from elements inside the root (tkinter.Tk) object.
But, after all this, my question is: Is this expected behaviour, or is this a bug within tkinter? If it is expected behaviour, why is it?
