4. Using else and finally in Exception Handling

Quiz: 0/5

When writing Python programs, you might run into situations where things don’t go as expected—like trying to open a file that doesn’t exist or dividing by zero. Python gives us a way to handle these errors using try-except blocks.

But did you know that you can also use else and finally to make your code even more reliable and readable? Let’s break it down!

When to use else in Try-Except

The else block is useful when you have code that should only run if no exceptions occur. Think of it like this:

• try: "I’ll attempt this risky operation."
• except: "Oops! If something goes wrong, I’ll handle it."
• else: "Great! Since nothing went wrong, I’ll continue with this extra step."

Example: Checking a number input

try:
    num = int(input("Enter a number: "))  # Trying to convert input to an integer
except ValueError:
    print("That's not a valid number!")  # Handles invalid input
else:
    print(f"Great! You entered {num}.")  # Runs only if no error occurs

Here, else ensures that the message "Great! You entered {num}." only appears when there’s no error.

The role of finally: Cleanup operations

The finally block is special because it always runs, no matter what happens—whether an error occurs or not. Think of it like this:

• try: "I’ll do something risky."
• except: "If something goes wrong, I’ll fix it."
• finally: "Regardless of what happened, I’ll clean up."

This is useful for actions like: 

• Closing files
• Closing database connections
• Releasing system resources

Example: Working with Files

try:
    file = open("data.txt", "r")  # Trying to open a file
    content = file.read()
    print(content)
except FileNotFoundError:
    print("Oops! The file doesn't exist.")
finally:
    print("Closing file...")
    file.close()  # Ensures the file is closed no matter what

Even if the file isn’t found, the finally block still runs, making sure we don’t leave the file open accidentally.

Why use else and finally together?

You can combine both for better control over your code.

Example: Safe Division

def safe_divide(a, b):
    try:
        result = a / b  # Attempt division
    except ZeroDivisionError:
        print("Error: Cannot divide by zero!")
    else:
        print(f"Result: {result}")  # Runs only if no error
    finally:
        print("End of operation.")  # Runs no matter what

safe_divide(10, 2)  # Works fine
safe_divide(10, 0)  # Triggers error, but 'finally' still runs

This ensures:

• Errors are handled properly.
• The success message appears only if division works.
• The cleanup message runs always.

Summary

• Use else when you want to execute some code only if no exception occurs.
• Use finally when you need to clean up resources, no matter what happens.