Python Simple Calculator Project with Solutions and Explanations

Last update on September 16 2025 12:33:24 (UTC/GMT +8 hours)

Calculator:

Input: User provides two numbers and selects an operation (addition, subtraction, multiplication, division).

Output: The result of the chosen operation.

Input and output values:

Input values:

Enter the first number: 5

Enter operation (+, -, *, /): +

Enter the second number: 3

Output value: Result: 8

Here are two different solutions for a basic calculator program in Python. Both solutions will accept user input for two numbers and an arithmetic operation (addition, subtraction, multiplication, or division) and then output the result.

Solution 1: Basic Approach using conditional statements

Code:

# Solution 1: Basic Approach Using Conditional Statements

# Get the first number from the user and convert it to a float
first_number = float(input("Enter the first number: "))

# Get the operation from the user (+, -, *, /)
operation = input("Enter operation (+, -, *, /): ")

# Get the second number from the user and convert it to a float
second_number = float(input("Enter the second number: "))

# Initialize a variable to store the result
result = None

# Perform the chosen operation using conditional statements
if operation == '+':
    # Addition
    result = first_number + second_number
elif operation == '-':
    # Subtraction
    result = first_number - second_number
elif operation == '*':
    # Multiplication
    result = first_number * second_number
elif operation == '/':
    # Division; check if the second number is not zero to avoid division by zero
    if second_number != 0:
        result = first_number / second_number
    else:
        # Handle division by zero error
        print("Error: Division by zero is not allowed.")
else:
    # Handle invalid operations
    print("Error: Invalid operation.")

# Print the result if a valid operation was performed
if result is not None:
    print(f"Result: {result}")

Output:

Enter the first number: 12
Enter operation (+, -, *, /): +
Enter the second number: 33
Result: 45.0

Enter the first number: 5
Enter operation (+, -, *, /): *
Enter the second number: 7
Result: 35.0

Enter the first number: 120
Enter operation (+, -, *, /): /
Enter the second number: 13
Result: 9.23076923076923

Enter the first number: 34
Enter operation (+, -, *, /): -
Enter the second number: 8
Result: 26.0

Explanation:

Uses if-elif-else statements to check the user's chosen operation and perform the corresponding arithmetic calculation.
Takes user input for two numbers and the desired operation, converts the numbers to floats, and checks for errors such as division by zero or an invalid operation.
This solution is straightforward but can become lengthy if more operations are added.

Solution 2: Using a Dictionary and Functions for Cleaner Code

Code:

# Solution 2: Using a Dictionary and Functions for Cleaner Code

# Define functions for each arithmetic operation
def add(x, y):
    """Function to perform addition"""
    return x + y

def subtract(x, y):
    """Function to perform subtraction"""
    return x - y

def multiply(x, y):
    """Function to perform multiplication"""
    return x * y

def divide(x, y):
    """Function to perform division, checks for division by zero"""
    if y == 0:
        return "Error: Division by zero is not allowed."
    return x / y

# Map operations to their corresponding functions using a dictionary
operations = {
    '+': add,
    '-': subtract,
    '*': multiply,
    '/': divide
}

# Get user input for the first number, operation, and second number
first_number = float(input("Enter the first number: "))
operation = input("Enter operation (+, -, *, /): ")
second_number = float(input("Enter the second number: "))

# Check if the chosen operation is valid
if operation in operations:
    # Retrieve the function corresponding to the chosen operation
    result = operations[operation](first_number, second_number)
    print(f"Result: {result}")
else:
    # Handle invalid operations
    print("Error: Invalid operation.")

Output:

Enter the first number: 12
Enter operation (+, -, *, /): +
Enter the second number: 33
Result: 45.0

Enter the first number: 5
Enter operation (+, -, *, /): *
Enter the second number: 7
Result: 35.0

Enter the first number: 120
Enter operation (+, -, *, /): /
Enter the second number: 13
Result: 9.23076923076923

Enter the first number: 34
Enter operation (+, -, *, /): -
Enter the second number: 8
Result: 26.0

Explanation:

Defines separate functions for each arithmetic operation (add, subtract, multiply, divide).
Uses a dictionary to map user inputs (+, -, *, /) to the corresponding functions.
When the user inputs an operation, the corresponding function is called from the dictionary, making the code more modular, organized, and easier to extend.
Handles errors such as division by zero and invalid operations in a clean, centralized way.

Note:
Both solutions accomplish the task, but Solution 2 is more modular, making it easier to maintain and extend for future improvements or additional operations.

Go to: