import tkinter as tk

class Example(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        super().__init__(parent, *args, **kwargs)

        self.buttons = []
        for i in range(1, 10+1):
            lab = i if i < 10 else 0
            button = tk.Button(self, text=f"{lab}",
                               command=lambda x=lab: self.addtocalcs(f"{x}"))
            self.buttons.append(button)

            row = (i-1) // 3
            col = (i-1) % 3
            if row == 3:    # to get row 3 button centered
                col = 1
            button.grid(row=row, column=col)

    def addtocalcs(self, value):
        print(f"addtocalcs called: {value=}")


root = tk.Tk()
root.resizable(False, False)
ex = Example(root)
ex.pack()
root.mainloop()