Python exception handling

Python exception handling:

Exception handling in Python allows you to deal with errors and unexpected situations gracefully. The primary keywords for exception handling are try, except, else, and finally.

Basic Exception Handling:

Basic exception handling in Python involves using the try and except blocks to catch and handle exceptions.

Here’s a simple example:

try:
# Code that may raise an exception
result = 10 / 0
except ZeroDivisionError:
# Code to handle the specific exception
print(“Cannot divide by zero!”)

In this example:

Within the try block resides the code that has the potential to raise an exception.
The except block catches the specific exception (ZeroDivisionError in this case) and executes the code inside the block.
If an exception occurs in the try block, the control transfers to the matching except block.

Various types of exceptions can be captured and managed appropriately:

try:
# Code that may raise an exception
result = int(“abc”)
except ValueError:
# Code to handle the specific exception
print(“Invalid conversion to integer!”)

In this example, the except block catches a ValueError if the conversion to an integer fails.

Capturing multiple exceptions within a unified except block is also achievable:

try:
# Code that may raise an exception
result = int(“abc”)
except (ValueError, TypeError):
# Code to handle multiple exceptions
print(“Invalid conversion to integer or incorrect type!”)

The except block is executed only if any of the specified exceptions occur in the corresponding try block.

These are the fundamental components of basic exception handling in Python. It allows you to gracefully handle errors and prevent your program from crashing when unexpected situations arise.

Handling Multiple Exceptions:

In Python, you can handle multiple exceptions in a single except block by specifying the exceptions within parentheses. This allows you to provide a common handling routine for different types of exceptions.

Here’s an example:

try:
# Code that may raise exceptions
result = int(“abc”)
result = 10 / 0
except (ValueError, ZeroDivisionError) as e:
# Code to handle multiple exceptions
print(f”An exception occurred: {e}”)

In this example:

The try block contains code that may raise either a ValueError or a ZeroDivisionError.
The except block catches both exceptions and prints a generic message along with the exception information.

You can catch as many exceptions as needed within the same except block, separating them with commas:

try:
# Code that may raise exceptions
result = int(“abc”)
result = 10 / 0
except (ValueError, TypeError) as ve:
# Code to handle ValueError or TypeError
print(f”ValueError or TypeError: {ve}”)
except ZeroDivisionError as zd:
# Code to handle ZeroDivisionError
print(f”ZeroDivisionError: {zd}”)
except Exception as e:
# Code to handle any other exceptions
print(f”An exception occurred: {e}”)

In this example:

The first except block handles both ValueError and TypeError.
The second except block handles ZeroDivisionError.
The third except block is a generic catch-all for any other exceptions.

Note that the order of except blocks matters. Python will execute the first block whose exception type matches the raised exception.

Handling multiple exceptions in one block is useful when you want to provide a common response to different types of errors or when you want to minimize redundant code.

Using ‘else’ with ‘try’ Exceptions:

In Python, the else block in conjunction with try and except allows you to specify a block of code that will be executed if no exceptions are raised in the corresponding try block.

The basic structure is as follows:

try:
# Code that may raise an exception
result = 10 / 2
except ZeroDivisionError:
# Code to handle the specific exception
print(“Cannot divide by zero!”)
else:
#Code to run in the absence of any exceptions
print(f”Result: {result}“)

In this example:

The try block contains code that might raise a ZeroDivisionError.
If a ZeroDivisionError occurs, the control transfers to the except block, and the specific exception handling code is executed.
If no exception occurs, the else block is executed, and it contains code that runs only when there is no exception.

Here’s another example with multiple exceptions and an else block:

try:
# Code that may raise exceptions
result = int(“42”)
except (ValueError, TypeError):
# Code to handle multiple exceptions
print(“Invalid conversion to integer or incorrect type!”)
else:
#Code to run if there are no exceptions
print(f”Result: {result}”)

In this case, if a ValueError or TypeError occurs, the except block is executed. If no exception occurs, the else block is executed.

The else block is optional, and its code is executed only when no exceptions are raised in the corresponding try block. It provides a way to separate the code that may raise exceptions from the code that should run only when there are no exceptions.

Using ‘finally’ Exception:

In Python, the finally block is used in conjunction with try and except to specify a block of code that will be executed whether an exception occurs or not.

The basic structure is as follows:

try:
# Code that may raise an exception
result = 10 / 2
except ZeroDivisionError:
# Code to handle the specific exception
print(“Cannot divide by zero!”)
else:
#Code to run in case no exceptions occur
print(f”Result: {result}”)
finally:
#Code to run irrespective of whether an exception occurred
print(“This will always be printed.”)

In this example:

The try block contains code that might raise a ZeroDivisionError.
If a ZeroDivisionError occurs, the control transfers to the except block, and the specific exception handling code is executed.
If no exception occurs, the else block is executed, and it contains code that runs only when there is no exception.
The finally block is always executed, regardless of whether an exception occurred. This block is commonly used for cleanup operations.

Here’s another example with an exception occurring:

try:
# Code that may raise an exception
result = 10 / 0
except ZeroDivisionError:
# Code to handle the specific exception
print(“Cannot divide by zero!”)
else:
#Code to run in the absence of any exceptions
print(f”Result: {result}”)
finally:
#Code to run irrespective of whether an exception occurred
print(“This will always be printed.”)

In this case, since a ZeroDivisionError occurs, the except block is executed, and then the finally block is also executed.

The finally block is often used for cleanup operations, such as closing files or releasing resources, ensuring that certain code is executed whether an exception occurs or not.

Handling Multiple Exceptions in One Block:

n Python, you can handle multiple exceptions in a single except block by specifying the exceptions within parentheses. This allows you to provide a common handling routine for different types of exceptions.

Here’s an example:

In this example:

The try block contains code that may raise either a ValueError or a ZeroDivisionError.
The except block catches both exceptions and prints a generic message along with the exception information.

You can catch as many exceptions as needed within the same except block, separating them with commas:

In this example:

The first except block handles both ValueError and TypeError.
The second except block handles ZeroDivisionError.
The third except block is a generic catch-all for any other exceptions.

Note that the order of except blocks matters. Python will execute the first block whose exception type matches the raised exception.

Handling multiple exceptions in one block is useful when you want to provide a common response to different types of errors or when you want to minimize redundant code.