Exception Handling: Making Your Code Error-Proof!

Imagine you’re playing a video game and suddenly hit a wall because you made the wrong move. The game doesn’t crash—it shows a message like, “Oops, wrong way!” and lets you try again. That’s what exception handling does in Python! It helps your program deal with unexpected situations without crashing.

Let’s dive in and learn how to handle these “oops moments” in Python!

🛑 What are Exceptions?

An exception is like an error that stops your program when something unexpected happens. For example:

• Dividing by zero (oops, math doesn’t like that!).
• Trying to open a file that doesn’t exist (oops, where’s that file?).
• Typing something unexpected, like words instead of numbers (oops, mismatch!).

🛠️ How Do We Handle Exceptions?

Python gives us a magic tool called try and except. Here’s the basic idea:

1. Try: Tell Python to try running a piece of code.
2. Except: Catch any error and decide what to do instead of crashing.

Example: Catching an Error

try:
    number = int(input("Enter a number: "))
    print("You entered:", number)
except ValueError:
    print("Oops! That's not a number.")

How it Works:

1. Python tries to turn your input into a number.
2. If you type something that’s not a number, Python catches the error and runs the except part.

🚧 Common Exception Types

Here are a few common errors Python can handle:

🎯 Handling Multiple Exceptions

Sometimes, different things can go wrong. You can handle them all separately.

try:
    num1 = int(input("Enter the first number: "))
    num2 = int(input("Enter the second number: "))
    result = num1 / num2
    print("Result is:", result)
except ZeroDivisionError:
    print("Oops! You can’t divide by zero.")
except ValueError:
    print("Oops! Please enter valid numbers.")

What Happens:

• If you divide by zero, the program says, “Oops! You can’t divide by zero.”
• If you type something other than a number, it says, “Oops! Please enter valid numbers.”

🧹 Finally: Cleaning Up!

The finally block lets you run code no matter what happens—whether there’s an error or not.

try:
    file = open("example.txt", "r")
    content = file.read()
    print(content)
except FileNotFoundError:
    print("Oops! File not found.")
finally:
    print("Finished trying to read the file.")

🌟 Raising Your Own Exceptions

Sometimes, you want to create your own “oops moments.” Use raise to throw an exception.

age = int(input("Enter your age: "))
if age < 0:
    raise ValueError("Age can’t be negative!")
else:
    print("Your age is:", age)

🏋️‍♂️ Practice Questions

1. Catch a Division Error

Write a program that asks the user to divide two numbers and handles a division by zero error.

Solution:

try:
    num1 = int(input("Enter numerator: "))
    num2 = int(input("Enter denominator: "))
    result = num1 / num2
    print("Result:", result)
except ZeroDivisionError:
    print("Oops! Denominator can’t be zero.")

2. File Not Found

Write a program that tries to open a file and catches the error if the file doesn’t exist.

Solution:

try:
    file = open("nonexistent_file.txt", "r")
    content = file.read()
    print(content)
except FileNotFoundError:
    print("Oops! File doesn’t exist.")

3. Raise Your Own Error

Write a program that raises an exception if someone enters an invalid age.

Solution:

try:
    age = int(input("Enter your age: "))
    if age < 0:
        raise ValueError("Age can’t be negative!")
    else:
        print("Your age is:", age)
except ValueError as e:
    print("Error:", e)