Python Built-in Exceptions – Master Error Types & Their Use

Introduction – Why Learn Built-in Exceptions?

When your Python program crashes with messages like IndexError, TypeError, or ZeroDivisionError, it’s not random—it’s Python raising a built-in exception.

Understanding these built-in exceptions helps you:

• Write cleaner, more defensive code
• Debug faster
• Handle errors gracefully with try...except

In this guide, you’ll learn:

• What built-in exceptions are in Python
• The most common exception types
• Their real-world causes and fixes
• How to use try...except to handle them
• Best practices for robust error handling

What Are Built-in Exceptions?

Built-in exceptions are standard error types raised by Python automatically when something goes wrong.

These exceptions are all subclasses of the built-in Exception class.

Most Common Built-in Exceptions

Here’s a quick table of frequently encountered exceptions:

Example: Handling Built-in Exceptions

ZeroDivisionError

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

ValueError

try:
    age = int("twenty")
except ValueError:
    print(" Invalid input. Please enter a number.")

FileNotFoundError

try:
    with open("data.txt", "r") as f:
        print(f.read())
except FileNotFoundError:
    print(" The file does not exist.")

Less Common but Important Exceptions

Special Exceptions (Subclass of BaseException)

These should rarely be caught unless necessary.

Best Practices

Tip: View All Built-in Exceptions

import builtins
print(dir(builtins))

You’ll see exceptions like ArithmeticError, LookupError, PermissionError, etc.

Summary – Recap & Next Steps

Python has dozens of built-in exceptions to handle invalid inputs, missing files, runtime logic errors, and more.

Key Takeaways:

• Built-in exceptions are raised automatically by Python
• Handle them using try...except for clean recovery
• Know the difference between common ones like ValueError, TypeError, and KeyError
• Avoid overly broad except: clauses—catch specific errors instead

Real-World Relevance:
Mastering built-in exceptions is essential for stable scripting, debugging, API development, and robust application design.

FAQ – Python Built-in Exceptions

How many built-in exceptions are there?

Python has 60+ built-in exceptions. You can see them via:

help("exceptions")

What is the parent of all exceptions?

All exceptions inherit from the base class Exception, which itself inherits from BaseException.

Can I catch multiple exceptions in one block?

Yes:

except (ValueError, TypeError) as e:
    print(e)

Should I catch BaseException?

No. Catch only Exception or its subclasses. Catching BaseException also catches SystemExit and KeyboardInterrupt, which should usually terminate the program.

What’s the difference between IndexError and KeyError?

• IndexError: List/tuple index is out of range.
• KeyError: Dictionary key doesn’t exist.