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Error and Exception in Python

23rd May 2023

Python uses errors and exceptions to deal with extraordinary circumstances that could arise while a programme is being executed. The usual flow of the programme is interrupted when an error or exception occurs, and Python raises an error or exception object to specify the error’s kind and specifics. Try-except blocks can be used to handle these mistakes and exceptions. Here is an illustration of how Python handles errors and exceptions:

# Example 1: Handling a specific exception

try:
    num1 = int(input("Enter a number: "))
    num2 = int(input("Enter another number: "))
    result = num1 / num2
    print("Result:", result)
except ZeroDivisionError:
    print("Error: Division by zero is not allowed.")

# Example 2: Handling multiple exceptions

try:
    num = int(input("Enter a number: "))
    result = 100 / num
    print("Result:", result)
except ValueError:
    print("Error: Invalid input. Please enter a valid number.")
except ZeroDivisionError:
    print("Error: Division by zero is not allowed.")

# Example 3: Handling any exception (generic exception)

try:
    file = open("nonexistent_file.txt", "r")
    content = file.read()
    file.close()
    print("Content:", content)
except Exception as e:
    print("Error:", str(e))

In the first example, a ,ZeroDivisionError, exception is handled if the user enters zero as the second number for division. In the second example, both 'ValueError‘ and ‘ZeroDivisionError' exceptions are handled, depending on the user’s input. In the third example, a generic ‘Exception‘ is caught, which can handle any type of exception. The 'as' keyword allows you to access the exception object, which can be useful for printing error messages or retrieving specific information about the error.

Python Exception Handling

22nd May 2023

In Python, handling exceptions is a technique for managing any faults or unusual circumstances that may arise while a programme is being executed. It enables you to gracefully handle some errors rather than having the programme end suddenly by allowing you to catch and handle them.

Python provides a built-in mechanism for exception handling using the try-except statement. The general syntax is as follows:

try:
    # Code block where an exception might occur
except ExceptionType1:
    # Code to handle the exception of type ExceptionType1
except ExceptionType2:
    # Code to handle the exception of type ExceptionType2
...
except:
    # Code to handle any other exceptions
else:
    # Code to execute if no exception occurs
finally:
    # Code that is always executed, regardless of whether an exception occurred or not

Here’s an explanation of the different parts:

  • The try block contains the code where you anticipate an exception might occur.
  • The except block is used to catch and handle specific types of exceptions. You can have multiple except blocks to handle different types of exceptions.
  • ExceptionType1, ExceptionType2, and so on, represent the specific types of exceptions you want to handle. For example, ValueError, TypeError, or IOError.
  • If an exception occurs in the try block and matches the specified exception type, the corresponding except block is executed. If no exception occurs, the except block is skipped.
  • You can have a generic except block without specifying the exception type. It will catch any exception that is not handled by the preceding except blocks. However, it is generally recommended to catch specific exceptions whenever possible.
  • The else block is optional and contains code that will be executed if no exception occurs in the try block.
  • The finally block is also optional and contains code that will always be executed, regardless of whether an exception occurred or not. It is typically used for cleanup tasks, such as closing files or releasing resources.

Here’s an example to illustrate how exception handling works:

try:
    num1 = int(input("Enter the numerator: "))
    num2 = int(input("Enter the denominator: "))
    result = num1 / num2
    print("Result:", result)
except ValueError:
    print("Invalid input. Please enter integers.")
except ZeroDivisionError:
    print("Cannot divide by zero.")
except Exception as e:
    print("An error occurred:", str(e))
else:
    print("Division operation completed successfully.")
finally:
    print("Exiting the program.")

In this example, if the user enters invalid input (non-integer values), a ValueError is raised and caught by the first except block. If the user enters zero as the denominator, a ZeroDivisionError is raised and caught by the second except block. Any other unhandled exceptions will be caught by the generic except block. The else block is executed if no exception occurs, and the finally block is always executed at the end, regardless of exceptions.

By using exception handling, you can ensure that your program handles errors gracefully, provides meaningful error messages, and continues executing even in the presence of exceptions