try/except in Python

Why use try/except?

Exceptions are normal in real programs:

• network failures
• missing files
• invalid user input

Instead of crashing, you can handle the problem and continue.

Basic try/except

basic_try_except.py

try:
    x = int(input("Enter a number: "))
    print(10 / x)
except Exception:
    print("Something went wrong")

This works, but it’s usually too broad.

Catch specific exceptions

specific_excepts.py

try:
    x = int(input("Enter a number: "))
    print(10 / x)
except ValueError:
    print("Please enter only digits.")
except ZeroDivisionError:
    print("Number can’t be 0.")

Catch multiple exception types

multi_except.py

try:
    x = int(input("Enter a number: "))
    print(10 / x)
except (ValueError, ZeroDivisionError) as e:
    print("Error:", e)

Capture the exception object

exception_object.py

try:
    int("abc")
except ValueError as e:
    print("Type:", type(e))
    print("Message:", e)

Best practices

• Catch the narrowest exception you can.
• Don’t silently ignore exceptions.
• Log exceptions in production systems.
• Avoid except Exception: unless you re-raise or report clearly.

Visualize it

try / except / else / finally is a small decision tree. Python runs the try body; if an exception is raised it jumps to a matching except; the else runs only when no exception occurred; and finally always runs, error or not:

diagram try / except / else / finally mermaid

  flowchart TD
  A([Enter try]) --> B["Run try body"]
  B --> C{"Exception raised?"}
  C -- yes --> D["Run matching except"]
  C -- no --> E["Run else block"]
  D --> F["Run finally (always)"]
  E --> F
  F --> G([Continue])

The except block runs only on an error, else only on success, and finally always runs.

🧪 Try It Yourself

Exercise 1 – Catch a ValueError

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Exercise 2 – Multiple Except Blocks

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Exercise 3 – Raise a Custom Exception

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