Python has a rich set of built-in exceptions designed to handle various types of runtime errors. These exceptions help you detect and respond to unexpected events during program execution.

In this guide, you'll learn:

• What built-in exceptions are

• A complete list of Python built-in exceptions

• An example for each exception

What Are Built-in Exceptions?

Built-in exceptions are predefined error classes in Python. They’re raised automatically (or manually using raise) when an error occurs during the execution of a program.

⚠️ Categories of Exceptions

Python exceptions can be broadly classified as:

• BaseException (base class)

  • SystemExit, KeyboardInterrupt, etc.

• Exception (most user-defined errors derive from here)

  • ArithmeticError, LookupError, etc.

List of Python Built-in Exceptions (with Examples)

Below is a list of the most commonly used built-in exceptions in Python, along with a short code example for each.

✅ 1. ArithmeticError

Base class for arithmetic errors.

try:
    x = 1 / 0
except ArithmeticError as e:
    print("Arithmetic error:", e)

✅ 2. ZeroDivisionError

Division by zero.

try:
    result = 5 / 0
except ZeroDivisionError as e:
    print("Cannot divide by zero:", e)

✅ 3. OverflowError

Math result too large to represent.

try:
    import math
    print(math.exp(1000))
except OverflowError as e:
    print("Overflow error:", e)

✅ 4. FloatingPointError

Rare; occurs in floating-point calculations.

import numpy as np
np.seterr(all='raise')
try:
    np.divide(1.0, 0.0)
except FloatingPointError as e:
    print("Floating point error:", e)

✅ 5. AssertionError

Raised by assert statement.

try:
    assert 2 + 2 == 5
except AssertionError as e:
    print("Assertion failed:", e)

✅ 6. AttributeError

Accessing an attribute that doesn’t exist.

try:
    "hello".fake_method()
except AttributeError as e:
    print("Attribute error:", e)

✅ 7. EOFError

Input ends unexpectedly.

try:
    input("Press Ctrl+D to raise EOFError: ")
except EOFError as e:
    print("EOF Error:", e)

✅ 8. ImportError

Import fails.

try:
    import non_existing_module
except ImportError as e:
    print("Import error:", e)

✅ 9. ModuleNotFoundError

Subclass of ImportError.

try:
    import fake_module
except ModuleNotFoundError as e:
    print("Module not found:", e)

✅ 10. IndexError

List index out of range.

try:
    lst = [1, 2, 3]
    print(lst[10])
except IndexError as e:
    print("Index error:", e)

✅ 11. KeyError

Accessing a non-existent key in a dictionary.

try:
    d = {"name": "Alice"}
    print(d["age"])
except KeyError as e:
    print("Key error:", e)

✅ 12. KeyboardInterrupt

Interrupt with Ctrl+C.

try:
    while True:
        pass
except KeyboardInterrupt:
    print("Keyboard Interrupt")

✅ 13. MemoryError

Out of memory.

try:
    a = ' ' * (10**10)
except MemoryError as e:
    print("Memory error:", e)

✅ 14. NameError

Using an undefined variable.

try:
    print(x)
except NameError as e:
    print("Name error:", e)

✅ 15. UnboundLocalError

Local variable referenced before assignment.

def func():
    try:
        print(x)
        x = 10
    except UnboundLocalError as e:
        print("Unbound local error:", e)
func()

✅ 16. OSError

Base class for OS-related errors.

try:
    open('/path/that/does/not/exist.txt')
except OSError as e:
    print("OS error:", e)

✅ 17. FileNotFoundError

File doesn't exist.

try:
    open("nofile.txt")
except FileNotFoundError as e:
    print("File not found:", e)

✅ 18. PermissionError

Lack of permissions.

try:
    open("/etc/shadow", "r")
except PermissionError as e:
    print("Permission denied:", e)

✅ 19. IsADirectoryError

Attempting to open a directory as a file.

try:
    open(".")  # Current directory
except IsADirectoryError as e:
    print("Is a directory:", e)

✅ 20. NotADirectoryError

Path component is not a directory.

try:
    import os
    os.listdir("file.txt/folder")
except NotADirectoryError as e:
    print("Not a directory:", e)

✅ 21. TypeError

Wrong data type used.

try:
    print("2" + 2)
except TypeError as e:
    print("Type error:", e)

✅ 22. ValueError

Right type, but wrong value.

try:
    int("abc")
except ValueError as e:
    print("Value error:", e)

✅ 23. RuntimeError

Generic error not covered by other exceptions.

try:
    raise RuntimeError("Something went wrong")
except RuntimeError as e:
    print("Runtime error:", e)

✅ 24. RecursionError

Too much recursion.

def recurse():
    return recurse()
try:
    recurse()
except RecursionError as e:
    print("Recursion error:", e)

✅ 25. StopIteration

Iterator is exhausted.

try:
    it = iter([1])
    next(it)
    next(it)
except StopIteration:
    print("StopIteration raised")

✅ 26. StopAsyncIteration

Async iterator is exhausted.

class AsyncCounter:
    async def __anext__(self):
        raise StopAsyncIteration

# Typically used with `async for`

✅ 27. IndentationError

Incorrect indentation.

# Cannot be caught in runtime; it is a syntax error.
# Example (invalid code):
# def func():
# print("No indent")

✅ 28. TabError

Mixing tabs and spaces.

(Syntax-level error — not catchable at runtime.)

✅ 29. SyntaxError

Invalid Python syntax.

try:
    eval("x === y")
except SyntaxError as e:
    print("Syntax error:", e)

✅ 30. SystemExit

Raised by sys.exit().

import sys
try:
    sys.exit()
except SystemExit:
    print("Exiting...")

✅ 31. BlockingIOError, ChildProcessError, ConnectionError, BrokenPipeError, TimeoutError, etc.

These are less common and are used for system-level and network operations.

Summary Table

✅ Best Practices

• Use try / except blocks to handle exceptions gracefully.

• Use specific exceptions when possible.

• Log the error messages for debugging.

• Avoid catching BaseException unless absolutely necessary.

Final Thoughts

Understanding Python’s built-in exceptions helps you write robust, fault-tolerant programs. Always handle exceptions responsibly and test edge cases in your applications.