What is Exception Handling?

When an error occurs, Python stops execution and raises an exception. Exception handling lets you catch those errors and decide how to respond, so your program continues running or fails gracefully.

Basic Syntax

try:
   # Code that might raise an exception
   risky_code()
except SomeException:
   # Code that runs if the exception occurs
   handle_error()

Example: ZeroDivisionError

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

Output:

You can't divide by zero!

Catching Multiple Exceptions

try:
   num = int("abc")
   result = 10 / 0
except ValueError:
   print("Invalid input!")
except ZeroDivisionError:
   print("Division by zero error!")

Output:

Invalid input!

Using else

The else block runs if no exception occurs.

try:
   result = 10 / 2
except ZeroDivisionError:
   print("Cannot divide by zero!")
else:
   print("Division successful:", result)

Output:

Division successful: 5.0

Using finally

The finally block always runs, whether an exception occurred or not.

try:
   result = 10 / 0
except ZeroDivisionError:
   print("Caught an error")
finally:
   print("This runs no matter what")

Output:

Caught an error
This runs no matter what

Raising Exceptions Manually

You can use the raise keyword to throw an exception.

x = -1
if x < 0:
   raise ValueError("Negative values are not allowed")

Output:

ValueError: Negative values are not allowed

Custom Exception Class

class MyError(Exception):
   pass
try:
   raise MyError("Something went wrong")
except MyError as e:
   print("Caught custom error:", e)

Summary Table