OOP Calculator Part 2 – Object Oriented Tkinter 5

In this video we’ll finish building our Calculator app with Object Oriented Tkinter and Python.

In the last video we built out the GUI for our app.

In this video we’ll create the functionality for the calculator…we’ll make it calculate!

Python Code: class_calc.py
(Github Code)

from tkinter import *

class App(Tk):
	def __init__(self):
		super().__init__()

		# Title, icon, size
		self.title("Tkinter.com - OOP Calculator")
		self.iconbitmap('images/codemy.ico')
		self.geometry('500x850')

		# Create Widgets
		self.my_label = Label(self, text="")
		self.my_label.pack(pady=(10,0))
		
		self.my_entry = Entry(self, width=25, font=("Helvetica", 24))
		self.my_entry.pack(pady=(0,10))

		# Create a new frame to hold the button
		My_frame(self)

	# Clear the entry box
	def clear(self):
		# Clear the box
		self.my_entry.delete(0, END)
		# clear the label
		self.my_label.config(text="")

	# Flip numbers positive or negative
	def pos_neg(self):
		if self.my_entry.get():
			if self.my_entry.get().startswith("-"):
				# Get whatever is in the entry box
				number = int(self.my_entry.get())
				# Delete Entry Box
				self.my_entry.delete(0, END)
				# Flip the number sign -/+
				self.my_entry.insert(0, (-1) * number)

			elif "+" not in self.my_entry.get() and "-" not in self.my_entry.get() and "*" not in self.my_entry.get() and "/" not in self.my_entry.get():
				# Get whatever is in the entry box
				number = int(self.my_entry.get())
				# Delete Entry Box
				self.my_entry.delete(0, END)
				# Flip the number sign -/+
				self.my_entry.insert(0, (-1) * number)

	# Pass the pressed Numbers to the entry box
	def num_press(self, num):
		self.my_entry.insert(END, num)

	# Get the math sign
	def signage(self, sign):
		# Check to make sure there's stuff in the box already
		if self.my_entry.get():
			# Add sign to end of the entry box
			self.my_entry.insert(END, sign)

	# Do the Math!!
	def mather(self):
		# Make sure the box is full
		if self.my_entry.get():
			# Define our equation
			equation = self.my_entry.get()
			# Output the equation to the label
			self.my_label.config(text=f'{equation} = {eval(equation)}')
			# Delete the box 
			self.my_entry.delete(0, END)
			# Output the answer to the box
			self.my_entry.insert(END, eval(equation))


# Button Frame Class
class My_frame(Frame):
	def __init__(self, parent):
		super().__init__(parent)
		# Pack the frame
		self.pack()
		# Define the buttons
		self.button_1 = Button(self, text="1", font=("Helvetica", 24), command = lambda: parent.num_press(1))
		self.button_2 = Button(self, text="2", font=("Helvetica", 24), command = lambda: parent.num_press(2))
		self.button_3 = Button(self, text="3", font=("Helvetica", 24), command = lambda: parent.num_press(3))

		self.button_4 = Button(self, text="4", font=("Helvetica", 24), command = lambda: parent.num_press(4))
		self.button_5 = Button(self, text="5", font=("Helvetica", 24), command = lambda: parent.num_press(5))
		self.button_6 = Button(self, text="6", font=("Helvetica", 24), command = lambda: parent.num_press(6))

		self.button_7 = Button(self, text="7", font=("Helvetica", 24), command = lambda: parent.num_press(7))
		self.button_8 = Button(self, text="8", font=("Helvetica", 24), command = lambda: parent.num_press(8))
		self.button_9 = Button(self, text="9", font=("Helvetica", 24), command = lambda: parent.num_press(9))

		self.button_0 = Button(self, text="0", font=("Helvetica", 24), command = lambda: parent.num_press(0))
		self.button_negative = Button(self, text="+/-", font=("Helvetica", 24), command=parent.pos_neg)
		self.button_equal = Button(self, text="=", font=("Helvetica", 24), command=parent.mather)

		self.button_plus = Button(self, text="+", font=("Helvetica", 24), command= lambda: parent.signage("+"))
		self.button_minus = Button(self, text="-", font=("Helvetica", 24), command= lambda: parent.signage("-"))
		self.button_multiply = Button(self, text="*", font=("Helvetica", 24), command= lambda: parent.signage("*"))

		self.button_divide = Button(self, text="/", font=("Helvetica", 24), command= lambda: parent.signage("/"))
		self.button_clear = Button(self, text="Clear", font=("Helvetica", 24), command=parent.clear)

		# Grid the buttons to the screen
		self.button_1.grid(row=0, column=0, ipadx=40, ipady=20, padx=(0, 10))
		self.button_2.grid(row=0, column=1, ipadx=40, ipady=20)
		self.button_3.grid(row=0, column=2, ipadx=40, ipady=20, padx=(10, 0))

		self.button_4.grid(row=1, column=0, ipadx=40, ipady=20, padx=(0, 10), pady=10)
		self.button_5.grid(row=1, column=1, ipadx=40, ipady=20, pady=10)
		self.button_6.grid(row=1, column=2, ipadx=40, ipady=20, padx=(10, 0), pady=10)

		self.button_7.grid(row=2, column=0, ipadx=40, ipady=20, padx=(0, 10), pady=10)
		self.button_8.grid(row=2, column=1, ipadx=40, ipady=20, pady=10)
		self.button_9.grid(row=2, column=2, ipadx=40, ipady=20, padx=(10, 0), pady=10)

		self.button_0.grid(row=3, column=0, ipadx=40, ipady=20, padx=(0, 10), pady=10)
		self.button_negative.grid(row=3, column=1, ipadx=31, ipady=20, pady=10)
		self.button_equal.grid(row=3, column=2, ipadx=40, ipady=20, padx=(10, 0), pady=10)

		self.button_plus.grid(row=4, column=0, ipadx=40, ipady=20, padx=(0, 10), pady=10)
		self.button_minus.grid(row=4, column=1, ipadx=40, ipady=20, pady=10)
		self.button_multiply.grid(row=4, column=2, ipadx=40, ipady=20, padx=(10, 0), pady=10)

		self.button_divide.grid(row=5, column=0, ipadx=42, ipady=20, padx=(0, 10), pady=10)
		self.button_clear.grid(row=5, column=1, columnspan=2, ipadx=84, ipady=20, padx=(10, 0), pady=10)

	
# Define and instantiate our app
app = App()
app.mainloop()