Tkinter RuntimeError: Too early to create image: no default root window

Question

So I'm trying to draw an image to a tkinter canvas in python, and keep getting the error in the title. I have a reference to tkinter.Tk() , I've set it as the canvas's master, I've packed the canvas, and run the mainloop. This all happens upon program start. Then, I call gui.drawentity() in main.py, which attempts to create an image and draw it to the canvas.

gui.py

root = tk.Tk()
canvas = tk.Canvas(root, bg="green")

canvas.pack(fill=tk.BOTH, expand=True)
root.mainloop()

def drawentity(entity):
    imgPath = data.getimagepath(entity.img, entity.imgType)
    img = None
    try:
        img = tk.PhotoImage(imgPath)
        canvas.create_image(entity.x, entity.y, img)
    except IOError as e: print(e)
    finally:
        if not isinstance(img, type(None)): img.close()

main.py

e = player.Player(100, 200, "Ball_Grayed.png", 3)
gui.drawentity(e)

data.py

 cd = os.path.join(os.getcwd(), "resources")
 def getimagepath(imgName, imgType):
     return os.path.join(cd, imgType, imgName)

When running py main.py , I get the following output:

File "S:\Users\Sean\Google Drive\cs\personal\BallAdventure\main.py", line 12, in <module>
    gui.drawentity(e)
  File "S:\Users\Sean\Google Drive\cs\personal\BallAdventure\gui.py", line 22, in drawentity
    img = tk.PhotoImage(imgPath)
  File "C:\Users\Sean\AppData\Local\Programs\Python\Python310\lib\tkinter\__init__.py", line 4093, in __init__
    Image.__init__(self, 'photo', name, cnf, master, **kw)
  File "C:\Users\Sean\AppData\Local\Programs\Python\Python310\lib\tkinter\__init__.py", line 4026, in __init__
    master = _get_default_root('create image')
  File "C:\Users\Sean\AppData\Local\Programs\Python\Python310\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

Everything looks fine to me, can anyone see what the problem is?

Answer 1

(see Nesi's comment)

It seems the tk.mainloop() call blocks (execution of the program halts there). I was only getting the error after exiting the window, which makes sense as the program essentially goes into a while True loop when mainloop() is called. Since I had been manually destroying the default root window, there was nothing to draw to upon continuing the code.

So, be careful where you put mainloop() , and know that it blocks .

( source/more info )