Table of Contents
- Necessary Libraries
- Imports
- Calculator App Class
- Creating Widgets
- Button Click Function
- Main Block
- Example
- Full Code
In today’s article, we are going to make a simple calculator App using the tkinter library in Python, let’s get started.
Necessary Libraries
For the code to function properly, make sure to install the tkinter library via the terminal or your command prompt:
$ pip install tk
Imports
import tkinter as tk
We start by importing the tkinter library as tk which allows us to use all its functions by using tk.
Calculator App Class
class CalculatorApp:
def __init__(self, root):
self.root = root
self.root.title("Simple Calculator - The Pycodes")
self.root.geometry("350x430")
self.root.resizable(False, False)
self.root.configure(bg="#1e1e1e")
self.equation = ""
self.create_widgets()
Next, we create a class which is a blueprint for our Calculator, then give our window a title set its geometry and background color, and disable its resizing, after that, we create instance Variables:
- One is
self.rootthat is going to store the main window and the other.
- Second,
self.equationthat is going to keep track of the mathematical expressions.
Creating Widgets
def create_widgets(self):
self.result_var = tk.StringVar()
entry_frame = tk.Frame(self.root, bg="#1e1e1e")
entry_frame.grid(row=0, column=0, columnspan=4, pady=20)
entry = tk.Entry(entry_frame, font=("Arial", 24), textvariable=self.result_var, bd=0, insertwidth=4, width=14,
justify="right", bg="#1e1e1e", fg="white")
entry.grid(row=0, column=0, ipady=8)
buttons = [
('7', 1, 0), ('8', 1, 1), ('9', 1, 2), ('/', 1, 3),
('4', 2, 0), ('5', 2, 1), ('6', 2, 2), ('*', 2, 3),
('1', 3, 0), ('2', 3, 1), ('3', 3, 2), ('-', 3, 3),
('C', 4, 0), ('0', 4, 1), ('=', 4, 2), ('+', 4, 3)
]
for (text, row, column) in buttons:
btn = tk.Button(self.root, text=text, font=("Arial", 18), width=5, height=2, bd=1, fg="#fff", bg="#2a2d36",
command=lambda t=text: self.button_click(t))
btn.grid(row=row, column=column, padx=5, pady=5)
self.root.bind('<Return>', lambda event: self.button_click('='))
Following that, we create and manage the visual parts that the user is gonna use.
- So as a start, we begin by using
StringVarwhich is atkintervariable to update the displayed result dynamically.
- Secondly, we create a frame where we are going to place the buttons then we make an entry widget where the result is going to be displayed.
- Thirdly we bound the entry widget to the
StringVarso that any changes in theself.result_varwill show in the entry widget.
- Fourth we create the buttons that hold the numbers and the mathematical signs and place them in a grid layout while giving them a specific styling and linking each of them to the
button_clickfunction which is triggered when the button is pressed.
Button Click Function
def button_click(self, value):
if value == 'C':
self.equation = ""
elif value == '=':
try:
result = str(eval(self.equation))
self.equation = result
except Exception as e:
result = "Error"
else:
self.equation += value
self.result_var.set(self.equation)
For this step, we define a function that gets called when any button is pressed performing a specific action based on the clicked button for example C clears the current equation, = evaluates the current equation, and if the evaluation is successful it displays the result. Otherwise, an error message is displayed in the entry widget, and so on for the other buttons.
Main Block
if __name__ == "__main__":
root = tk.Tk()
app = CalculatorApp(root)
root.mainloop()
Lastly, this part initializes the main window and keeps it running in a loop so that the user can use the different elements of the graphical user interface until he chooses to exit the main window.
Example
This is the final result you get once you run the code:
Full Code
import tkinter as tk
class CalculatorApp:
def __init__(self, root):
self.root = root
self.root.title("Simple Calculator - The Pycodes")
self.root.geometry("350x430")
self.root.resizable(False, False)
self.root.configure(bg="#1e1e1e")
self.equation = ""
self.create_widgets()
def create_widgets(self):
self.result_var = tk.StringVar()
entry_frame = tk.Frame(self.root, bg="#1e1e1e")
entry_frame.grid(row=0, column=0, columnspan=4, pady=20)
entry = tk.Entry(entry_frame, font=("Arial", 24), textvariable=self.result_var, bd=0, insertwidth=4, width=14,
justify="right", bg="#1e1e1e", fg="white")
entry.grid(row=0, column=0, ipady=8)
buttons = [
('7', 1, 0), ('8', 1, 1), ('9', 1, 2), ('/', 1, 3),
('4', 2, 0), ('5', 2, 1), ('6', 2, 2), ('*', 2, 3),
('1', 3, 0), ('2', 3, 1), ('3', 3, 2), ('-', 3, 3),
('C', 4, 0), ('0', 4, 1), ('=', 4, 2), ('+', 4, 3)
]
for (text, row, column) in buttons:
btn = tk.Button(self.root, text=text, font=("Arial", 18), width=5, height=2, bd=1, fg="#fff", bg="#2a2d36",
command=lambda t=text: self.button_click(t))
btn.grid(row=row, column=column, padx=5, pady=5)
self.root.bind('<Return>', lambda event: self.button_click('='))
def button_click(self, value):
if value == 'C':
self.equation = ""
elif value == '=':
try:
result = str(eval(self.equation))
self.equation = result
except Exception as e:
result = "Error"
else:
self.equation += value
self.result_var.set(self.equation)
if __name__ == "__main__":
root = tk.Tk()
app = CalculatorApp(root)
root.mainloop()
Happy Coding!
Learn also: How to Make a Simple Interest Calculator using Python
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