What are Exceptions in Python - Discuss All Types of Python Exception

Exceptions in Python help manage errors and keep your program running smoothly. When something goes wrong, like dividing by zero or trying to open a missing file, exceptions let you know there’s a problem. So this article is here to explain what exceptions are, as well as the different types like built-in and custom ones. Learning these techniques will help make your code stronger and better at dealing with errors.

Understanding Exceptions in Python

Exceptions in Python are errors that happen when the program runs, like trying to divide by zero or open a file that doesn't exist. Python uses a try-except block to handle these errors and keep the program running. The try block has the code that might cause an error and the except block deals with the error if it happens. You can also use finally to run code no matter what, and raise to create an error on purpose. Handling exceptions well makes your code stronger and less likely to crash.

Why Exceptions Occur?

Exceptions can occur for a variety of reasons, including:

• User Input Errors: This happens when the user gives data the program can't handle.
• Logic Errors: Occurs when there's a mistake in the code's logic.
• Resource Errors: Arise when a needed resource (like a file or network) isn't available.
• Hardware Failures: This happens when the hardware can't complete an operation.

Types of Exceptions in Python

Python provides a comprehensive set of built-in exceptions. In fact, these can be categorized into two main types:

1. Built-in Exceptions
2. User-defined Exceptions

Built-in Exceptions

Python's built-in exceptions are defined in the standard library and cover a wide range of error conditions. So, here is a Python exceptions list of some common built-in exceptions:

• Exception:? The main class for all built-in errors.
• ArithmeticError:? The main class for math-related errors like ZeroDivisionError, OverflowError, and FloatingPointError.
• AttributeError: This happens when a variable's attribute is missing or can't be set.
• EOFError:? Occurs when the input() function reaches the end of the file.
• ImportError: This happens when Python can't find a module or a name in a module.
• IndexError: This happens when you try to access an index that doesn't exist in a list or other sequence.
• KeyError:? Occurs when a key isn't found in a dictionary.
• KeyboardInterrupt:? Raised when the user presses Control-C or Delete.
• MemoryError: This happens when the program runs out of memory.
• NameError:? Occurs when a variable name isn't found.
• OSError: This happens when a system-related error occurs, like FileNotFoundError, PermissionError, or TimeoutError.
• RuntimeError:? A general error when no other category fits.
• TypeError: This happens when an operation is used on the wrong type of object.
• ValueError:? Occurs when a function gets an argument of the right type but with a bad value.

User-defined Exceptions

In addition to built-in exceptions in Python, it allows you to define your own exceptions by creating a new class derived from the Exception class. This is useful for handling all Python exceptions that are unique to your application.

class CustomError(Exception):

????pass

def check_value(value):

????if value < 0:

????????raise CustomError("Value cannot be negative")

try:

????check_value(-1)

except CustomError as e:

????print(e)

Exception Handling in Python

Effective exception handling is key to building reliable applications. Python provides a robust mechanism to handle exceptions using the try, except, else, and finally blocks.

Basic Exception Handling

The try block lets you test a block of code for errors. The except block lets you handle the error. The else block executes if no exceptions are raised, and the finally block executes regardless of whether an exception occurred or not.

try:

????x = 1 / 0

except ZeroDivisionError:

????print("Cannot divide by zero")

else:

????print("No exceptions occurred")

finally:

????print("Execution completed")

Handling Multiple Exceptions

You can handle multiple exceptions in Python by specifying multiple except blocks.

try:

????value = int("abc")

except ValueError:

????print("ValueError: Invalid literal for int()")

except TypeError:

????print("TypeError: Invalid operation")

Catching All Exceptions

You can catch all exceptions by using the base Exception class, but this is generally discouraged as it can make debugging difficult.

try:

????result = some_function()

except Exception as e:

????print(f"An error occurred: {e}")

Using raise to Propagate Exceptions

In some cases, you may want to catch an exception and then re-raise it, allowing it to propagate up the call stack.

def example_function():

????try:

????????x = 1 / 0

????except ZeroDivisionError:

????????print("Handling ZeroDivisionError")

????????raise

try:

????example_function()

except ZeroDivisionError:

????print("Caught in the outer block")

The assert Statement

The assert statement is used to test if a condition is true. If the condition is false, an AssertionError exception is raised.

x = -1

assert x >= 0, "x must be non-negative"

If you are interested in learning more about exception handling in Python, then enrolling on a Python certification course could be a great opportunity for you to gain a deeper understanding of exceptions and could also be very beneficial for kickstarting your career in the field of software development.

All Python Exceptions List

Here is a comprehensive list of exceptions in Python to reference when handling errors:

• ArithmeticError
• AssertionError
• AttributeError
• EOFError
• ImportError
• IndexError
• KeyError
• KeyboardInterrupt
• MemoryError
• NameError
• OSError
• OverflowError
• RuntimeError
• StopIteration
• SyntaxError
• IndentationError
• TabError
• SystemError
• SystemExit
• TypeError
• UnboundLocalError
• ValueError
• ZeroDivisionError

Best Practices for Exception Handling in Python

Exception handling in Python is essential for writing reliable and easy-to-maintain code. Properly managing exceptions helps your program recover from errors smoothly and gives useful feedback to the user. Here are some best practices for handling exceptions in python:

• Be Specific: Catch specific errors instead of using a general Exception.
• Use Multiple Except Blocks: Handle different errors with different except blocks.
• Avoid Silent Failures: Log or report errors when you catch them.
• Use Finally for Cleanup: Always release resources or clean up in a final block.
• Document Exceptions: Clearly document which errors your functions might raise.
• Create Custom Exceptions: Use custom errors for special situations in your application.

Conclusion

In conclusion, handling exceptions in Python is crucial for building strong and dependable programs. By knowing the built-in exceptions, creating your exceptions, and using good error-handling practices.? You can keep your code running smoothly and handle problems effectively. As well as always catch specific errors, use different except blocks for different issues, and make sure errors are reported. Using finally for cleanup and documenting exceptions will make your code more reliable and easier to maintain.