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Main Function Parameters and Return Value for Calculator in Python

In this exercise, you will develop a Python program that performs arithmetic operations such as addition, subtraction, multiplication, or division by analyzing command line arguments. This exercise is perfect for practicing command-line input handling, arithmetic operations, and error handling in Python. By implementing this program, you will gain hands-on experience in handling command-line input, performing arithmetic operations, and using error handling in Python. This exercise not only reinforces your understanding of command-line input handling but also helps you develop efficient coding practices for managing user interactions.



Group

Mastering Functions in Python

Objective

Develop a Python program that performs arithmetic operations such as addition, subtraction, multiplication, or division by analyzing command line arguments. For example, running the program with calc 5 + 379 should calculate the sum. The input must consist of two numbers and an operator, with the allowed operators being +, -, *, or /.

The program should return the following error codes:
1 if the number of arguments is not exactly 3
2 if the second argument is not a valid operator
3 if the first or third argument is not a valid number
0 if the operation is successfully performed

Example Python Exercise

 Copy Python Code 
import sys  # Importing the sys module to access command line arguments

# Function to check if a string can be converted to a valid number
def is_valid_number(value):
    try:
        float(value)  # Try to convert the string to a float
        return True  # If successful, return True
    except ValueError:
        return False  # If conversion fails, return False

# Checking if the correct number of arguments are passed
if len(sys.argv) != 4:
    print("Error: Invalid number of arguments.")  # Print error message for incorrect number of arguments
    sys.exit(1)  # Exit with error code 1

# Extracting the numbers and operator from the command line arguments
num1 = sys.argv[1]  # First argument (number1 as string)
operator = sys.argv[2]  # Second argument (operator)
num2 = sys.argv[3]  # Third argument (number2 as string)

# Check if the operator is valid
if operator not in ['+', '-', '*', '/']:
    print("Error: Invalid operator.")  # Print error message for invalid operator
    sys.exit(2)  # Exit with error code 2

# Check if both arguments are valid numbers
if not is_valid_number(num1) or not is_valid_number(num2):
    print("Error: Invalid number.")  # Print error message for invalid number
    sys.exit(3)  # Exit with error code 3

# Convert the numbers to floats for calculation
num1 = float(num1)
num2 = float(num2)

# Performing the operation based on the operator
if operator == '+':
    result = num1 + num2  # Perform addition
elif operator == '-':
    result = num1 - num2  # Perform subtraction
elif operator == '*':
    result = num1 * num2  # Perform multiplication
elif operator == '/':
    if num2 == 0:
        print("Error: Division by zero.")  # Handle division by zero
        sys.exit(3)  # Exit with error code 3
    result = num1 / num2  # Perform division

# Print the result of the operation
print(f"The result of {num1} {operator} {num2} is: {result}")
sys.exit(0)  # Exit with success code 0

 Output

Case 1:
python calc.py 5 + 379
The result of 5.0 + 379.0 is: 384.0

Case 2:
python calc.py 10 / 0
Error: Division by zero.

Case 3:
python calc.py 25 & 4
Error: Invalid operator.

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