view.py

import tkinter as tk
from tkinter import ttk


class View(tk.Tk):

    PAD = 10

    MAX_BUTTONS_PER_ROW = 4

    button_captions = [
        'C', '+/-', '%', '/',
        7, 8, 9, '*',
        4, 5, 6, '-',
        1, 2, 3, '+',
        0, '.', '='
    ]

    def __init__(self, controller):
        """

        :param controller:
        """
        super().__init__()
        self.title('PyTkCalc')
        self.controller = controller
        self.value_var = tk.StringVar()

        self._make_main_frame()
        self._make_entry()
        self._make_buttons()
        self._center_window()

    def main(self):
        self.mainloop()
        print('In main of view')

    def _make_main_frame(self):
        self.main_frm = ttk.Frame(self)
        self.main_frm.pack(padx=self.PAD, pady=self.PAD)

    def _make_entry(self):
        ent = ttk.Entry(
            self.main_frm, justify='right', textvariable=self.value_var, state='disabled'
        )
        ent.pack(fill="x")

    def _make_buttons(self):
        outer_frm = ttk.Frame(self.main_frm)
        outer_frm.pack()

        frm = ttk.Frame(outer_frm)
        frm.pack()

        buttons_in_row = 0
        for caption in self.button_captions:
            if buttons_in_row == self.MAX_BUTTONS_PER_ROW:
                frm = ttk.Frame(outer_frm)
                frm.pack()
                buttons_in_row = 0

            btn = ttk.Button(
                frm, text=caption, command=(lambda button=caption: self.controller.on_button_click(button))
                             )
            btn.pack(side="left")
            buttons_in_row += 1

    def _center_window(self):
        self.update()
        width = self.winfo_width()
        height = self.winfo_height()
        x_offset = (self.winfo_screenwidth() - width) // 2
        y_offset = (self.winfo_screenheight() - height) // 2
        self.geometry(
            f'{width}x{height}+{x_offset}+{y_offset}'
        )