Python Exception Handling Explained (try, except, finally)

Things go wrong in real programs — a user types text where a number is expected, a file doesn't exist, a network call times out. Without handling, any of these crashes your entire program with an unhandled error (a "traceback"). Python's try/except/finally structure lets you anticipate specific failures and respond to them gracefully instead of letting the whole program die.

Basic try / except

Code that might fail goes inside try. If an error occurs, Python jumps straight to the matching except block instead of crashing.

try:
    num = int(input("Enter a number: "))
    result = 10 / num
    print(f"Result: {result}")
except ZeroDivisionError:
    print("You can't divide by zero.")
except ValueError:
    print("That wasn't a valid number.")

Output:

// Input: 0
You can't divide by zero.

// Input: abc
That wasn't a valid number.

Catching specific exception types like ZeroDivisionError or ValueError — rather than a bare except: that catches everything — is important: a bare except silently swallows bugs you probably want to know about, like a typo in a variable name.

else and finally

An else block runs only if the try block succeeded with no exception. A finally block always runs, whether an exception happened or not — commonly used for cleanup, like closing a file or a network connection.

try:
    num = int(input("Enter a number: "))
    result = 10 / num
except ZeroDivisionError:
    print("Can't divide by zero.")
else:
    print(f"Success: {result}")
finally:
    print("Done attempting the calculation.")

Output:

// Input: 5
Success: 2.0
Done attempting the calculation.

Catching Multiple Exceptions in One Block

If several exception types should be handled the same way, group them in a tuple instead of repeating the handling code.

try:
    data = {"a": 1}
    value = data["b"] / 0
except (KeyError, ZeroDivisionError) as e:
    print(f"Something went wrong: {type(e).__name__}")

Output:

Something went wrong: KeyError

Once you're comfortable with Python's built-in exceptions, the natural next step is defining your own custom exceptions for errors specific to your application. You can also see a complete worked example with multiple except blocks in the exception handling program example.