Tkinter: windows without title bar but resizable

The problem is, the window is resizable, but when you turn on overrideredirect you lose any sort of header or edge that you can grab in order to resize the window. The only solution is to implement resizing yourself. You can add your own borders, or add mouse bindings that work when the mouse is near an edge.

This answer shows how to move such a window: Python/Tkinter: Mouse drag a window without borders, eg. overridedirect(1)

Here's a short example that illustrates resizing. It has only barely been tested on OSX but should work on any platform. It uses python2, though it should work with python3 just by changing the import statements.

import Tkinter as tk
import ttk

class Example(tk.Tk):
    def __init__(self):
        tk.Tk.__init__(self)
        self.floater = FloatingWindow(self)

class FloatingWindow(tk.Toplevel):
    def __init__(self, *args, **kwargs):
        tk.Toplevel.__init__(self, *args, **kwargs)
        self.overrideredirect(True)
        self.wm_geometry("400x400")

        self.label = tk.Label(self, text="Grab the lower-right corner to resize")
        self.label.pack(side="top", fill="both", expand=True)

        self.grip = ttk.Sizegrip(self)
        self.grip.place(relx=1.0, rely=1.0, anchor="se")
        self.grip.lift(self.label)
        self.grip.bind("<B1-Motion>", self.OnMotion)


    def OnMotion(self, event):
        x1 = self.winfo_pointerx()
        y1 = self.winfo_pointery()
        x0 = self.winfo_rootx()
        y0 = self.winfo_rooty()
        self.geometry("%sx%s" % ((x1-x0),(y1-y0)))
        return

app=Example()
app.mainloop()