Exceptions in Python

In Python, exceptions are events that represent an error, and which interrupt the normal execution flow of a program.

Exceptions are used to signal exceptional conditions that require special handling (for example, division by zero, reference to an undefined variable, or opening a file that does not exist).

Base Exceptions

In Python, all exceptions inherit from the base Exceptions.

• Exception: Base class for all exceptions in Python, except those that indicate interpreter exit.
• BaseException: Base class for all exceptions, including those used to control program termination.

Standard Exceptions in Python

Python includes a large number of standard exceptions that cover various errors and exceptional conditions. Let’s go through a list of some of the most common standard exceptions.

Runtime Error Exceptions

try:
    result = 1 / 0
except ZeroDivisionError as e:
    print(f"Division by zero error: {e}")

• ArithmeticError: Base class for numeric errors
• ZeroDivisionError: Raised when attempting to divide by zero
• OverflowError: Raised when a numeric calculation exceeds the maximum allowed limit
• FloatingPointError: Raised when an error occurs in a floating-point operation

Input/Output Operation Exceptions

try:
    with open('non_existent_file.txt', 'r') as file:
        content = file.read()
except FileNotFoundError as e:
    print(f"File not found: {e}")

• IOError: Base class for input/output errors
• FileNotFoundError: Raised when a file or directory is not found
• PermissionError: Raised when an operation lacks the appropriate permissions

Argument Exceptions

try:
    number = int("abc")
except ValueError as e:
    print(f"Value error: {e}")

• TypeError: Raised when an operation or function is applied to an object of inappropriate type
• ValueError: Raised when an operation or function receives an argument with the correct type but an inappropriate value

Variable and Attribute Exceptions

try:
    print(undefined_variable)
except NameError as e:
    print(f"Variable name not found: {e}")

• NameError: Raised when a local or global variable is not found
• AttributeError: Raised when trying to access an attribute that does not exist on an object

System Exceptions

• SystemError: Raised when an internal error in Python is detected
• KeyboardInterrupt: Raised when program execution is interrupted by user input (for example, Ctrl+C)