Exception Handling

The following convention should be followed for Exception handling:

• Exception handling is a must and should be mitigated.
• Do not use bare except or except Exception which catches all the exception.
  • Always be specific on exception. E.g. catch only FileNotFoundError if you are say moving a file.
• User Defined Exceptions:
  • Write your custom error only when your error is not described or fulfilled by internal exceptions.
  • Create custom Exception class primarily suffixing it with Error such as MyCustomError(Exception) and use it.
  • Always use Exception as your parent class for user defined exceptions. Donot use BaseException.
• Add traceback to your mitigation. i.e. either logging or mails. Donot pass.
• The try block should be specific to desired exception. Donot use huge code chunk in try. Use else if needed.

    try:
        value = int(some_str)
    except ValueError: # when not using exception object
        WHEN some_str IS not valid as value.
    except TypeError:
        WHEN some_str IS OTHER TYPE such as [], ()
    else: #can be avoided if exceptions are handled and returned. This is in context to try block.
        DO SOMETHING WITH VALUE
    
    try:
        value = int(some_str)
    except (ValueError, TypeError) as error:
        HANDLE BOTH exception and use exception object
    else: # If needed
        do something when try succeeds.
    finally:
        codebase to run anyway

• finally can be used if you need to run the block whatever the case. context can be used in many cases to avoid finally.
• sys.exc_info and traceback can be used for traceback.
• Please read this on exceptions handling internals and leaks when referencing exceptions.