Exception Handling with try/except

Sometimes, programs crash because of unexpected errors — like dividing by zero or accessing a file that doesn’t exist.
Instead of crashing, we can use exception handling to deal with those errors gracefully.

Python provides four key tools:

• try
• except
• else
• finally

1. try and except

Wrap risky code in a try block. If an error happens, Python jumps to the except block.

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Oops! You can't divide by zero.")

Explanation:

• The division causes an error.
• Python skips the crash and shows a message instead.

2. Handling Multiple Error Types

You can catch different types of exceptions in separate except blocks.

try:
    num = int("abc")
except ValueError:
    print("That’s not a valid number.")
except TypeError:
    print("Type mismatch.")

Explanation:

• This handles a ValueError caused by int("abc").

3. else and finally

• else runs only if no error occurs.
• finally runs no matter what, even if there’s an error.

try:
    value = int("42")
except ValueError:
    print("Conversion failed.")
else:
    print("Conversion succeeded:", value)
finally:
    print("Done checking.")

Explanation:

• else confirms success.
• finally is good for cleanup (like closing files or connections).

Summary

Keyword	Purpose
try	Run risky code
except	Handle specific errors
else	Runs if no exception occurred
finally	Always runs — useful for cleanup

What’s Next?

In the next lesson, we’ll learn how to read and write files to store and retrieve data.