Raising Exceptions
This chapter dives into how and when to raise exceptions, and how you can create custom exceptions to handle specific situations more gracefully in your applications.
How and When to Raise Exceptions
Exceptions in Python should be raised to signal that an error condition has occurred, making it impossible for a function or method to perform its intended task. This is especially useful in situations where simply returning a None
or a similar value could be ambiguous and might not adequately convey that an error has occurred.
Raising a Standard Exception
To raise an exception in Python, you use the raise statement. Here's a simple example:
In this example, a ValueError is raised if the birth_year
is greater than the current year, indicating that the provided birth year is invalid.
Creating Custom Exceptions
While Python's built-in exceptions cover many different scenarios, sometimes you may need to define your own exceptions to clearly express an error condition specific to your domain.
Defining Custom Exceptions
Custom exceptions are typically derived from the built-in Exception class or one of its subclasses. Here's how you can define a custom exception:
Hope you remember the inheritance concept from the OOP 😉
Here's a practical example of how custom exceptions are used. Don't worry about the else
and as
keywords in the example; we'll cover those in the next chapter.
Code Description
RegistrationError
: A base class for other registration-related exceptions. It is derived from Python's built-in Exception class. This organization helps in categorizing all registration-related exceptions under a single umbrella, which simplifies exception handling.UsernameTooShort
: A specific exception is raised when a username is shorter than the required minimum length of 6 characters.PasswordTooWeak
: Another specific exception for when a password does not meet the minimum strength criteria, defined here as being at least 8 characters long.
Functions for Registration validation
validate_username(username)
: This function checks if the provided username is less than 6 characters long. If it is, it raises a UsernameTooShort exception with a message indicating that the username must be at least 6 characters long.validate_password(password)
: Similarly, this function checks the length of the password, and if it's less than 8 characters, it raises a PasswordTooWeak exception with a corresponding message.
Registration Functionregister_user(username, password)
: This is the main function where user registration takes place. It calls the validation functions for both the username and the password.- If the username or password does not meet the criteria, the respective custom exception is raised and caught in the except block. The error message is then printed, indicating why registration failed.
- If no exceptions are raised, the else block executes, printing a success message indicating the user has been registered successfully.
¿Todo estuvo claro?
Contenido del Curso
Python Advanced Concepts
Python Advanced Concepts
Raising Exceptions
This chapter dives into how and when to raise exceptions, and how you can create custom exceptions to handle specific situations more gracefully in your applications.
How and When to Raise Exceptions
Exceptions in Python should be raised to signal that an error condition has occurred, making it impossible for a function or method to perform its intended task. This is especially useful in situations where simply returning a None
or a similar value could be ambiguous and might not adequately convey that an error has occurred.
Raising a Standard Exception
To raise an exception in Python, you use the raise statement. Here's a simple example:
In this example, a ValueError is raised if the birth_year
is greater than the current year, indicating that the provided birth year is invalid.
Creating Custom Exceptions
While Python's built-in exceptions cover many different scenarios, sometimes you may need to define your own exceptions to clearly express an error condition specific to your domain.
Defining Custom Exceptions
Custom exceptions are typically derived from the built-in Exception class or one of its subclasses. Here's how you can define a custom exception:
Hope you remember the inheritance concept from the OOP 😉
Here's a practical example of how custom exceptions are used. Don't worry about the else
and as
keywords in the example; we'll cover those in the next chapter.
Code Description
RegistrationError
: A base class for other registration-related exceptions. It is derived from Python's built-in Exception class. This organization helps in categorizing all registration-related exceptions under a single umbrella, which simplifies exception handling.UsernameTooShort
: A specific exception is raised when a username is shorter than the required minimum length of 6 characters.PasswordTooWeak
: Another specific exception for when a password does not meet the minimum strength criteria, defined here as being at least 8 characters long.
Functions for Registration validation
validate_username(username)
: This function checks if the provided username is less than 6 characters long. If it is, it raises a UsernameTooShort exception with a message indicating that the username must be at least 6 characters long.validate_password(password)
: Similarly, this function checks the length of the password, and if it's less than 8 characters, it raises a PasswordTooWeak exception with a corresponding message.
Registration Functionregister_user(username, password)
: This is the main function where user registration takes place. It calls the validation functions for both the username and the password.- If the username or password does not meet the criteria, the respective custom exception is raised and caught in the except block. The error message is then printed, indicating why registration failed.
- If no exceptions are raised, the else block executes, printing a success message indicating the user has been registered successfully.
¿Todo estuvo claro?