Chapter 10: Error Handling and Exceptions

 

10.1 Introduction to
Errors and Exceptions

10.1.1 Understanding
errors and exceptions in Python

Explanation: Errors and
exceptions are part of the normal execution flow in Python. They occur when
something goes wrong during the program's execution, and they can be handled to
prevent program termination.

Example:

 

python

///Example

# ZeroDivisionError:
division by zero

result = 1 / 0

10.1.2 Common types of
built-in exceptions

Explanation: Python
provides various built-in exception types to handle specific types of errors,
such as ValueError, TypeError, and FileNotFoundError. Each exception type
represents a specific error condition.

Example:

 

python

///Example

# ValueError: invalid
literal for int() with base 10: 'abc'

number = int('abc')

10.1.3 The try-except
block

Explanation: The
try-except block allows for the handling of exceptions. Code that may raise an
exception is placed within the try block, and the desired exception handling is
specified in the except block.

Example:

 

python

///Example

try:

    result = 1 / 0

except
ZeroDivisionError:

    print("Error: Division by zero
occurred")

10.2 Handling
Exceptions

10.2.1 Handling
specific exceptions

Explanation: Specific
exceptions can be caught and handled individually using multiple except blocks,
allowing for different handling strategies based on the specific exception
type.

Example:

 

python

///Example

try:

    result = 1 / 0

except
ZeroDivisionError:

    print("Error: Division by zero
occurred")

except ValueError:

    print("Error: Invalid value
encountered")

10.2.2 Handling
multiple exceptions

Explanation: Multiple
exceptions can be handled using a single except block by specifying multiple
exception types within parentheses.

Example:

 

python

///Example

try:

    result = int('abc')

except (ValueError,
TypeError):

    print("Error: Invalid value
encountered")

10.2.3 Handling all
exceptions

Explanation: An except
block without an explicitly specified exception type can be used to handle any
exception that occurs within the try block. It allows for a generic exception
handling strategy.

Example:

 

python

///Example

try:

    result = 1 / 0

except:

    print("An error occurred")

10.3 The else and
finally Blocks

10.3.1 The else block

Explanation: The else
block is executed if no exceptions occur within the try block. It provides a
way to specify code that should run only if the try block completes without
raising an exception.

Example:

 

python

///Example

try:

    result = 10 / 2

except
ZeroDivisionError:

    print("Error: Division by zero
occurred")

else:

    print("Result:", result)

10.3.2 The finally
block

Explanation: The
finally block is always executed, regardless of whether an exception occurred
or not. It is commonly used to release resources or perform cleanup operations.

Example:

 

python

///Example

file = open("file.txt",
"r")

try:

    content = file.read()

    print(content)

except:

    print("An error occurred")

finally:

    file.close()

10.4 Raising Exceptions

10.4.1 Raising
exceptions manually

Explanation: Exceptions
can be raised manually using the raise statement. It allows for the creation
and raising of custom exceptions to indicate specific error conditions.

Example:

 

python

///Example

def divide(a, b):

    if b == 0:

        raise ValueError("Division by
zero")

    return a / b

 

try:

    result = divide(1, 0)

except ValueError as e:

    print("Error:", str(e))

10.4.2 Creating custom
exception classes

Explanation: Custom
exception classes can be created by inheriting from the built-in Exception
class. This allows for the creation of custom exception hierarchies to handle
specific types of errors.

Example:

 

python

///Example

class
CustomException(Exception):

    pass

 

try:

    raise CustomException("Custom
exception occurred")

except
CustomException as e:

    print("Error:", str(e))