Exception Handling

When Python hits an error it can't recover from on its own, it raises an exception — if nothing catches it, the program crashes and prints a traceback. try/except lets you catch specific exceptions and decide what to do instead of crashing.

try:
    age = int(input("Enter your age: "))
    print(f"Next year you'll be {age + 1}")
except ValueError:
    print("That's not a valid number")

Catching specific exceptions

Always catch the most specific exception type you can — a bare except: catches everything, including typos and KeyboardInterrupt, which usually hides real bugs instead of handling them.

data = {"CodeWithMunnaX": 250_000}

try:
    print(data["CodeWithHarry"])
except KeyError:
    print("Channel not found")
except TypeError:
    print("Keys must be hashable")

You can catch multiple exception types in one clause with a tuple: except (KeyError, TypeError):.

else and finally

• else runs only if the try block didn't raise anything.
• finally always runs, whether an exception happened or not — used for cleanup (closing a file, releasing a resource).

try:
    result = 10 / 2
except ZeroDivisionError:
    print("Can't divide by zero")
else:
    print("No error, result is", result)
finally:
    print("This always runs")

Raising your own exceptions

Use raise to signal that something is wrong in your own code — often paired with a custom, descriptive message.

def subscribe(subscriber_count):
    if subscriber_count < 0:
        raise ValueError("Subscriber count can't be negative")
    return subscriber_count + 1

try:
    subscribe(-5)
except ValueError as e:
    print("Rejected:", e)

Common built-in exceptions