One-expression calculator.

ocalc.py

# A Tkinter calculator in a single Python *expression*
# See https://www.reddit.com/r/Python/comments/ojab0n/i_see_your_17_loc_calculator_and_i_raise_you_a/
(tk := __import__("tkinter")) and (bt_draw := lambda k, c, l: (bt := tk.Button(w, text=k, command=lambda: bt_press(k), width=6)) and bt.grid(column=c, row=l)) and (update := lambda t: d.config(text=t)) and (bt_press := lambda k: update("") if k == "C" else update(d["text"][:-1]) if k == "<" else update(str(round(eval(d["text"]), 6))) if k == "=" else update(d["text"] + k)) and (w := tk.Tk()) and w.title("TKalc") or (d := tk.Label(w, text="")) and d.grid(column=0, row=0, columnspan=5) or [bt_draw(k, n%4 + 1, n//4 + 1) for n, k in enumerate("()C<789/456*123-.0=+")] and w.mainloop()