Python GUI Calculator

main.py

"""
Copyright 2023 Yonathan Tesfaye

Github: https://github.com/TheRealYT

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

   Basic gui calculator based on python libraries, tested on Python v3.9.0 on windows 10
"""
from tkinter import *
from tkinter import ttk
import re

width = 280
height = 420
boxHeight = 70
buttonWidth = 70
buttonHeight = 70


class App(Frame):

    def __init__(self, master=None):
        Frame.__init__(self, master)
        self.init()

        self.operator = StringVar()
        self.num_old = StringVar()
        self.num_input = StringVar()

        self.operators = {
            '/': (lambda a, b: "ZeroDivisionError" if (b == 0) else a / b),
            '*': (lambda a, b: a * b),
            '-': (lambda a, b: a - b),
            '+': (lambda a, b: a + b),
            '%': (lambda a, b: a % b)
        }

        ttk.Label(master, textvariable=self.num_input, anchor="e", background="#fff", padding=15).place(
            height=boxHeight, width=width)
        Label(master, textvariable=self.num_old, anchor="center", background="#fff").place(x=0, y=0)
        Label(master, textvariable=self.operator, anchor="center", background="#fff").place(x=width - 15, y=0)

        self.col_row_buttons([
            [
                Button(master, text="C", fg="black", command=lambda: self.exec("CLEAR")),
                Button(master, text="7", fg="black", command=lambda: self.exec("7")),
                Button(master, text="4", fg="black", command=lambda: self.exec("4")),
                Button(master, text="1", fg="black", command=lambda: self.exec("1")),
                Button(master, text="+/-", fg="black", command=lambda: self.exec("SIGN"))
            ],
            [
                Button(master, text="CE", fg="black", command=lambda: self.exec("CLEAR_E")),
                Button(master, text="8", fg="black", command=lambda: self.exec("8")),
                Button(master, text="5", fg="black", command=lambda: self.exec("5")),
                Button(master, text="2", fg="black", command=lambda: self.exec("2")),
                Button(master, text="0", fg="black", command=lambda: self.exec("0"))
            ],
            [
                Button(master, text="%", fg="black", command=lambda: self.exec("%")),
                Button(master, text="9", fg="black", command=lambda: self.exec("9")),
                Button(master, text="6", fg="black", command=lambda: self.exec("6")),
                Button(master, text="3", fg="black", command=lambda: self.exec("3")),
                Button(master, text=".", fg="black", command=lambda: self.exec("."))
            ],
            [
                Button(master, text="/", fg="black", command=lambda: self.exec("/")),
                Button(master, text="*", fg="black", command=lambda: self.exec("*")),
                Button(master, text="-", fg="black", command=lambda: self.exec("-")),
                Button(master, text="+", fg="black", command=lambda: self.exec("+")),
                Button(master, text="=", fg="black", command=lambda: self.exec("="))
            ]
        ], 0, 0)

    @staticmethod
    def row_buttons(buttons, offset_x=0, offset_y=0, col=1, row=1):
        for i in range(len(buttons)):
            buttons[i].place(x=((i * col) + offset_x) * buttonWidth, y=boxHeight + (offset_y * buttonHeight),
                             width=buttonWidth * col, height=buttonHeight * row)

    @staticmethod
    def col_buttons(buttons, offset_x=0, offset_y=0, col=1, row=1):
        for i in range(len(buttons)):
            buttons[i].place(x=offset_x * buttonWidth, y=boxHeight + (((i * row) + offset_y) * buttonHeight),
                             width=buttonWidth * col, height=buttonHeight * row)

    def row_col_buttons(self, buttons, offset_x=0, offset_y=0, col=1, row=1):
        for i in range(len(buttons)):
            self.row_buttons(buttons[i], offset_x=offset_x, offset_y=offset_y + i, col=col, row=row)

    def col_row_buttons(self, buttons, offset_x=0, offset_y=0, col=1, row=1):
        for i in range(len(buttons)):
            self.col_buttons(buttons[i], offset_x=offset_x + i, offset_y=offset_y, col=col, row=row)

    def exec(self, value=""):
        if re.match(r'^[a-z]+$', self.num_input.get().lower()):
            self.num_input.set("")

        if re.match(r'^[0-9.]+$', value):
            if self.num_input.get() == "0":
                if value == "0":
                    return
                else:
                    self.num_input.set("")
            elif value == ".":
                if "." in self.num_input.get():
                    return
                elif self.num_input.get() == "":
                    self.num_input.set("0")

            self.num_input.set(self.num_input.get() + value)
        elif re.match(r'^[/*\-+%=]$', value):
            if value == "=":
                if self.operator.get() != "" and self.num_input.get() != "":
                    self.calc()
            elif self.num_input.get() != "" or self.num_old.get() != "":
                self.operator.set(value)
                if self.num_old.get() == "":
                    self.num_old.set(self.num_input.get())
                    self.num_input.set("")
        elif value == "SIGN":
            if self.num_input.get() != "":
                self.num_input.set(str(-1 * self.parse(self.num_input.get())))
        elif value == "CLEAR":
            self.num_old.set("")
            self.num_input.set("")
            self.operator.set("")
        elif value == "CLEAR_E":
            self.num_input.set("")

    def calc(self):
        a = self.parse(self.num_old.get())
        b = self.parse(self.num_input.get())

        self.num_old.set("")
        self.num_input.set(self.operators[self.operator.get()](a, b))
        self.operator.set("")

    @staticmethod
    def parse(num_str):
        if num_str == "":
            return 0
        return float(num_str) if ("." in num_str) else int(num_str)

    def init(self):
        self.master.title("Calculator")

        self.master.minsize(width, height)
        self.master.maxsize(width, height)


# create the application
root = Tk()
app = App(root)

# start the program
app.mainloop()