import tkinter as tk

x=300
y=200

def click(event):
  global x,y
  canvas.create_oval(x-20,y-20,x+20,y+20,fill="white",width=0)
  x=event.x
  y=event.y
  canvas.create_oval(x-20,y-20,x+20,y+20,fill="red",width=0)



root=tk.Tk()
root.geometry("600x400")

canvas=tk.Canvas(root,width=600,height=400,bg="white")
canvas.place(x=0,y=0)

canvas.bind("<Button-1>",click)
root.mainloop()