Create and read sanitized email
Input
User(' Alice ', 'ALICE@EXAMPLE.COM', 30).email
Output
alice@example.com
Email is trimmed and lowercased.
Full lesson preview
Validate and Sanitize Data in a Property Setter
Practice using @property setters to validate and sanitize attributes like username, email, and age.
Python practice16 minMethods & PropertiesIntermediateLast updated April 7, 2026
Problem statement
Implement a User class with three attributes: username, email, and age. Use @property decorators to control access:
- username: sanitize by stripping leading/trailing whitespace and capitalizing the first letter (e.g. ' alice ' -> 'Alice'). If the sanitized username is empty, raise ValueError.
- email: sanitize by trimming whitespace and lowercasing. Validate with a basic check: it must contain exactly one '@' and at least one '.' in the domain portion (after the '@'). If invalid, raise ValueError.
- age: accept integer-like values (ints or digit strings) and store as an int. If conversion is not possible or the result is negative, raise ValueError.
Provide a summary() helper that returns a string like "Alice <alice@example.com> (30)".
Task
Implement property getters and setters that sanitize input (strip/normalize) and validate values, converting types when appropriate.
Examples
Input format
Constructor parameters: username (str), email (str), age (int or numeric string).
Output format
Accessors return sanitized values: username (str), email (str), age (int).
Constraints
- username must be a non-empty string after trimming
- email must include one '@' and at least one '.' after '@'
- age must convert to a non-negative integer
- On invalid input, raise ValueError
Samples
Sample 1
Input
User(' bob ', 'bob@site.com', '0').username
Output
Bob
Username trimmed and capitalized; age string converted to int 0.