Do tkinter's PhotoImages really require a root window? Why?

Question

I'm trying to create a small class to represent vital information about various GIFs that I want the software to handle. Here's my code:

from PIL import Image
import tkinter as tk

class ListifiedGif:
    """Class containing list of frames and number of frames from GIF."""
    def __init__(self, filename):
        gif = Image.open(filename)
        self.frame_count = gif.n_frames
        self.frame_list = [tk.PhotoImage(file = filename,
                                         format = f'gif -index {i}')
                                         for i in range(gif.n_frames)]

When I insert the following at the end of the file, I get an error.

testimg = ListifiedGif('E:\\Development\\desktop\\img\\walking_negative.gif')

print(testimg.frame_count)
print(testimg.frame_list)

... and here's the error:

Traceback (most recent call last):
  File "<module1>", line 13, in <module>
  File "<module1>", line 9, in __init__
  File "<module1>", line 9, in <listcomp>
  File "C:\Program Files\Python39\lib\tkinter\__init__.py", line 4064, in __init__
    Image.__init__(self, 'photo', name, cnf, master, **kw)
  File "C:\Program Files\Python39\lib\tkinter\__init__.py", line 3997, in __init__
    master = _get_default_root('create image')
  File "C:\Program Files\Python39\lib\tkinter\__init__.py", line 297, in _get_default_root
    raise RuntimeError(f"Too early to {what}: no default root window")
RuntimeError: Too early to create image: no default root window

Why is it necessary to declare a root window in order to create an image? Is there a way around this so that I can simply return the list of frames (as a series of PhotoImages from tkinter) without having to worry about precisely what the window that the image will be used in looks like?

Thanks in advance for your time.

You can hide the `tk.Tk()` by using: `.withdraw()` and then show it using `.deiconify()` — TheLizzard, Aug 11 '21 at 16:56
That's really interesting. Thanks for mentioning that. I may find it useful. — MattFunke, Aug 12 '21 at 15:24

score 1 · Answer 1 · answered Aug 11 '21 at 15:59

1

Why is it necessary to declare a root window in order to create an image?

Because the underlying tcl/tk interpreter needs to be initialized before you can create images, and it is the creation of the root window that does the initialization.

Is there a way around this

No. You have to create a root window before you can create images using tkinter.

answered Aug 11 '21 at 15:59

Bryan Oakley

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Thank you for your insight. I gather, then, that it's not possible to perform that initialization without creating a root window. That's too bad; I think that means that I'll have to come up with ways to modify that root window after information is read in. – MattFunke Aug 11 '21 at 17:54
@MattFunke: _"I'll have to come up with ways to modify that root window after information is read in."_ - that shouldn't be difficult. You don't have to do any special to update the window after it has been created. – Bryan Oakley Aug 11 '21 at 19:19

Do tkinter's PhotoImages really require a root window? Why?

1 Answers1