Calculator GUI

Abstract

Create a fully functional calculator with a graphical user interface that supports basic arithmetic operations, decimal numbers, error handling, and clear functionality. This project demonstrates GUI design, event handling, and mathematical expression evaluation.

Prerequisites

Python 3.6 or above
Text Editor or IDE
Basic understanding of Python syntax
Knowledge of Tkinter for GUI development
Familiarity with arithmetic operations
Understanding of event-driven programming

Getting Started

Create a new project

Create a new project folder and name it calculatorGUIcalculatorGUI.
Create a new file and name it calculatorgui.pycalculatorgui.py.
Open the project folder in your favorite text editor or IDE.
Copy the code below and paste it into your calculatorgui.pycalculatorgui.py file.

Write the code

Add the following code to your calculatorgui.pycalculatorgui.py file.

⚙️ Calculator GUI

Calculator GUI

# Calculator with GUI using Tkinter
 
from tkinter import *
 
solution = ""
 
def press(num):
    global solution
    solution = solution + str(num)
    equation.set(solution)
    
def equalpress():
    try:
        global solution
        total = str(eval(solution))
        equation.set(total)
        solution = ""
    except:
        equation.set(" error ")
        solution = ""
        
def clear():
    global solution
    solution = ""
    equation.set("")
    
if __name__ == "__main__":
    gui = Tk()
    gui.configure(background="light green")
    gui.title("Calculator")
    gui.geometry("270x150")
    equation = StringVar()
    expression_field = Entry(gui, textvariable=equation)
    expression_field.grid(columnspan=4, ipadx=70)
    equation.set('enter your expression')
    button1 = Button(gui, text=' 1 ', fg='black', bg='gray',
                     command=lambda: press(1), height=1, width=7)
    button1.grid(row=2, column=0)
    button2 = Button(gui, text=' 2 ', fg='black', bg='gray',
                     command=lambda: press(2), height=1, width=7)
    button2.grid(row=2, column=1)
    button3 = Button(gui, text=' 3 ', fg='black', bg='gray',
                     command=lambda: press(3), height=1, width=7)
    button3.grid(row=2, column=2)
    button4 = Button(gui, text=' 4 ', fg='black', bg='gray',
                     command=lambda: press(4), height=1, width=7)
    button4.grid(row=3, column=0)
    button5 = Button(gui, text=' 5 ', fg='black', bg='gray',
                     command=lambda: press(5), height=1, width=7)
    button5.grid(row=3, column=1)
    button6 = Button(gui, text=' 6 ', fg='black', bg='gray',
                     command=lambda: press(6), height=1, width=7)
    button6.grid(row=3, column=2)
    button7 = Button(gui, text=' 7 ', fg='black', bg='gray',
                     command=lambda: press(7), height=1, width=7)
    button7.grid(row=4, column=0)
    button8 = Button(gui, text=' 8 ', fg='black', bg='gray',
                     command=lambda: press(8), height=1, width=7)
    button8.grid(row=4, column=1)
    button9 = Button(gui, text=' 9 ', fg='black', bg='gray',
                     command=lambda: press(9), height=1, width=7)
    button9.grid(row=4, column=2)
    button0 = Button(gui, text=' 0 ', fg='black', bg='gray',
                     command=lambda: press(0), height=1, width=7)
    button0.grid(row=5, column=0)
    plus = Button(gui, text=' + ', fg='black', bg='gray',
                  command=lambda: press("+"), height=1, width=7)
    plus.grid(row=2, column=3)
    minus = Button(gui, text=' - ', fg='black', bg='gray',
                   command=lambda: press("-"), height=1, width=7)
    minus.grid(row=3, column=3)
    multiply = Button(gui, text=' * ', fg='black', bg='gray',
                      command=lambda: press("*"), height=1, width=7)
    multiply.grid(row=4, column=3)
    divide = Button(gui, text=' / ', fg='black', bg='gray',
                    command=lambda: press("/"), height=1, width=7)
    divide.grid(row=5, column=3)
    equal = Button(gui, text=' = ', fg='black', bg='gray',
                   command=equalpress, height=1, width=7)
    equal.grid(row=5, column=2)
    clear = Button(gui, text='Clear', fg='black', bg='gray',
                   command=clear, height=1, width=7)
    clear.grid(row=5, column='1')
    Decimal= Button(gui, text='.', fg='black', bg='gray',
                    command=lambda: press('.'), height=1, width=7)
    Decimal.grid(row=6, column=0)
    gui.mainloop()

Calculator GUI

# Calculator with GUI using Tkinter
 
from tkinter import *
 
solution = ""
 
def press(num):
    global solution
    solution = solution + str(num)
    equation.set(solution)
    
def equalpress():
    try:
        global solution
        total = str(eval(solution))
        equation.set(total)
        solution = ""
    except:
        equation.set(" error ")
        solution = ""
        
def clear():
    global solution
    solution = ""
    equation.set("")
    
if __name__ == "__main__":
    gui = Tk()
    gui.configure(background="light green")
    gui.title("Calculator")
    gui.geometry("270x150")
    equation = StringVar()
    expression_field = Entry(gui, textvariable=equation)
    expression_field.grid(columnspan=4, ipadx=70)
    equation.set('enter your expression')
    button1 = Button(gui, text=' 1 ', fg='black', bg='gray',
                     command=lambda: press(1), height=1, width=7)
    button1.grid(row=2, column=0)
    button2 = Button(gui, text=' 2 ', fg='black', bg='gray',
                     command=lambda: press(2), height=1, width=7)
    button2.grid(row=2, column=1)
    button3 = Button(gui, text=' 3 ', fg='black', bg='gray',
                     command=lambda: press(3), height=1, width=7)
    button3.grid(row=2, column=2)
    button4 = Button(gui, text=' 4 ', fg='black', bg='gray',
                     command=lambda: press(4), height=1, width=7)
    button4.grid(row=3, column=0)
    button5 = Button(gui, text=' 5 ', fg='black', bg='gray',
                     command=lambda: press(5), height=1, width=7)
    button5.grid(row=3, column=1)
    button6 = Button(gui, text=' 6 ', fg='black', bg='gray',
                     command=lambda: press(6), height=1, width=7)
    button6.grid(row=3, column=2)
    button7 = Button(gui, text=' 7 ', fg='black', bg='gray',
                     command=lambda: press(7), height=1, width=7)
    button7.grid(row=4, column=0)
    button8 = Button(gui, text=' 8 ', fg='black', bg='gray',
                     command=lambda: press(8), height=1, width=7)
    button8.grid(row=4, column=1)
    button9 = Button(gui, text=' 9 ', fg='black', bg='gray',
                     command=lambda: press(9), height=1, width=7)
    button9.grid(row=4, column=2)
    button0 = Button(gui, text=' 0 ', fg='black', bg='gray',
                     command=lambda: press(0), height=1, width=7)
    button0.grid(row=5, column=0)
    plus = Button(gui, text=' + ', fg='black', bg='gray',
                  command=lambda: press("+"), height=1, width=7)
    plus.grid(row=2, column=3)
    minus = Button(gui, text=' - ', fg='black', bg='gray',
                   command=lambda: press("-"), height=1, width=7)
    minus.grid(row=3, column=3)
    multiply = Button(gui, text=' * ', fg='black', bg='gray',
                      command=lambda: press("*"), height=1, width=7)
    multiply.grid(row=4, column=3)
    divide = Button(gui, text=' / ', fg='black', bg='gray',
                    command=lambda: press("/"), height=1, width=7)
    divide.grid(row=5, column=3)
    equal = Button(gui, text=' = ', fg='black', bg='gray',
                   command=equalpress, height=1, width=7)
    equal.grid(row=5, column=2)
    clear = Button(gui, text='Clear', fg='black', bg='gray',
                   command=clear, height=1, width=7)
    clear.grid(row=5, column='1')
    Decimal= Button(gui, text='.', fg='black', bg='gray',
                    command=lambda: press('.'), height=1, width=7)
    Decimal.grid(row=6, column=0)
    gui.mainloop()

Save the file.
Run the following command to run the application.

command

C:\Users\username\Documents\calculatorGUI> python calculatorgui.py
[Calculator GUI Opens]
- Click number buttons to input values
- Click operation buttons (+, -, *, /) for calculations
- Click "=" to get the result
- Click "Clear" to reset the calculator
Example: 5 + 3 = 8

command

C:\Users\username\Documents\calculatorGUI> python calculatorgui.py
[Calculator GUI Opens]
- Click number buttons to input values
- Click operation buttons (+, -, *, /) for calculations
- Click "=" to get the result
- Click "Clear" to reset the calculator
Example: 5 + 3 = 8

 
## Explanation
 
1. The `from tkinter import *` statement imports all Tkinter components for creating the GUI.
2. The `solution = ""` creates a global variable to store the current mathematical expression.
3. The `equation = StringVar()` creates a Tkinter string variable for the display.
4. The `def press(num):` function handles button presses and updates the expression.
5. The `def equalpress():` function evaluates the mathematical expression using eval().
6. The `def clear():` function resets the calculator by clearing the expression.
7. The `gui = Tk()` creates the main window for the calculator.
8. The `expression_field = Entry()` creates the display field for showing expressions and results.
9. The number buttons (0-9) are created with lambda functions to pass their values.
10. The operation buttons (+, -, *, /) handle arithmetic operations.
11. The grid layout system organizes buttons in a calculator-style arrangement.
12. Error handling displays "error" when invalid expressions are entered.
 
## Next Steps
 
Congratulations! You have successfully created a Calculator GUI in Python. Experiment with the code and see if you can modify the application. Here are a few suggestions:
- Add advanced mathematical functions (sin, cos, tan, log, sqrt)
- Implement memory functions (M+, M-, MR, MC)
- Add keyboard input support
- Create a history feature to track calculations
- Implement bracket support for complex expressions
- Add a scientific calculator mode
- Create different themes and color schemes
- Add sound effects for button presses
- Implement percentage calculations
 
## Conclusion
 
In this project, you learned how to create a Calculator GUI in Python using Tkinter. You also learned about GUI design, event handling, and mathematical expression evaluation. You can find the source code on [GitHub](https://github.com/Ravikisha/PythonCentralHub/blob/main/projects/beginners/calculatorgui.py)
 
 
 
## Code Explanation
 
### Global State Management
```python title="calculatorgui.py" showLineNumbers{1}
solution = ""
 
def press(num):
    global solution
    solution = solution + str(num)
    equation.set(solution)

 
## Explanation
 
1. The `from tkinter import *` statement imports all Tkinter components for creating the GUI.
2. The `solution = ""` creates a global variable to store the current mathematical expression.
3. The `equation = StringVar()` creates a Tkinter string variable for the display.
4. The `def press(num):` function handles button presses and updates the expression.
5. The `def equalpress():` function evaluates the mathematical expression using eval().
6. The `def clear():` function resets the calculator by clearing the expression.
7. The `gui = Tk()` creates the main window for the calculator.
8. The `expression_field = Entry()` creates the display field for showing expressions and results.
9. The number buttons (0-9) are created with lambda functions to pass their values.
10. The operation buttons (+, -, *, /) handle arithmetic operations.
11. The grid layout system organizes buttons in a calculator-style arrangement.
12. Error handling displays "error" when invalid expressions are entered.
 
## Next Steps
 
Congratulations! You have successfully created a Calculator GUI in Python. Experiment with the code and see if you can modify the application. Here are a few suggestions:
- Add advanced mathematical functions (sin, cos, tan, log, sqrt)
- Implement memory functions (M+, M-, MR, MC)
- Add keyboard input support
- Create a history feature to track calculations
- Implement bracket support for complex expressions
- Add a scientific calculator mode
- Create different themes and color schemes
- Add sound effects for button presses
- Implement percentage calculations
 
## Conclusion
 
In this project, you learned how to create a Calculator GUI in Python using Tkinter. You also learned about GUI design, event handling, and mathematical expression evaluation. You can find the source code on [GitHub](https://github.com/Ravikisha/PythonCentralHub/blob/main/projects/beginners/calculatorgui.py)
 
 
 
## Code Explanation
 
### Global State Management
```python title="calculatorgui.py" showLineNumbers{1}
solution = ""
 
def press(num):
    global solution
    solution = solution + str(num)
    equation.set(solution)

Maintains the current expression as a global string, updating the display whenever new input is added.

Expression Evaluation

calculatorgui.py

def equalpress():
    try:
        global solution
        total = str(eval(solution))
        equation.set(total)
        solution = ""
    except:
        equation.set(" error ")
        solution = ""

calculatorgui.py

def equalpress():
    try:
        global solution
        total = str(eval(solution))
        equation.set(total)
        solution = ""
    except:
        equation.set(" error ")
        solution = ""

Uses Python’s eval()eval() function to calculate mathematical expressions with proper error handling for invalid operations.

GUI Layout with Grid System

calculatorgui.py

gui = Tk()
gui.configure(background="light green")
gui.title("Calculator")
gui.geometry("270x150")
 
expression_field = Entry(gui, textvariable=equation)
expression_field.grid(columnspan=4, ipadx=70)

calculatorgui.py

gui = Tk()
gui.configure(background="light green")
gui.title("Calculator")
gui.geometry("270x150")
 
expression_field = Entry(gui, textvariable=equation)
expression_field.grid(columnspan=4, ipadx=70)

Creates a structured calculator layout using Tkinter’s grid system for organized button placement.

Number and Operation Buttons

calculatorgui.py

button1 = Button(gui, text=' 1 ', fg='black', bg='gray',
                 command=lambda: press(1), height=1, width=7)
button1.grid(row=2, column=0)
 
plus = Button(gui, text=' + ', fg='black', bg='gray',
              command=lambda: press("+"), height=1, width=7)
plus.grid(row=2, column=3)

calculatorgui.py

button1 = Button(gui, text=' 1 ', fg='black', bg='gray',
                 command=lambda: press(1), height=1, width=7)
button1.grid(row=2, column=0)
 
plus = Button(gui, text=' + ', fg='black', bg='gray',
              command=lambda: press("+"), height=1, width=7)
plus.grid(row=2, column=3)

Implements individual buttons for numbers (0-9) and operators (+, -, *, /) with lambda functions for command handling.

Clear Functionality

calculatorgui.py

def clear():
    global solution
    solution = ""
    equation.set("")

calculatorgui.py

def clear():
    global solution
    solution = ""
    equation.set("")

Provides a reset function to clear both the current expression and the display.

Features

Standard Calculator Layout: Traditional button arrangement
Basic Arithmetic Operations: Addition, subtraction, multiplication, division
Decimal Number Support: Includes decimal point for floating-point calculations
Real-Time Display: Shows current expression as it’s being built
Error Handling: Displays “error” for invalid expressions
Clear Function: Reset calculator to initial state
Responsive Interface: Immediate visual feedback for button presses

Next Steps

Enhancements

Add advanced mathematical functions (sin, cos, tan, log)
Implement memory functions (M+, M-, MR, MC)
Add keyboard input support
Create calculation history feature
Implement parentheses for complex expressions
Add percentage calculations
Include square root and power functions
Implement better error messages

Learning Extensions

Study mathematical expression parsing
Explore custom number formatting
Learn about calculator algorithms
Practice with advanced GUI layouts
Understand operator precedence rules
Explore scientific calculator features

Educational Value

This project teaches:

GUI Development: Creating interactive interfaces with buttons and displays
Event Handling: Managing user interactions and button clicks
State Management: Maintaining application state across user actions
String Manipulation: Building and processing mathematical expressions
Error Handling: Managing invalid input and calculation errors
Grid Layout System: Organizing GUI components in structured layouts
Lambda Functions: Using anonymous functions for button commands
Expression Evaluation: Understanding how calculators process mathematical expressions

Perfect for understanding GUI application development, user interface design, and mathematical computation in programming.

Calculator GUI

Abstract

Prerequisites

Getting Started

Create a new project

Write the code

Expression Evaluation

GUI Layout with Grid System

Number and Operation Buttons

Clear Functionality

Features

Next Steps

Enhancements

Learning Extensions

Educational Value

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