Կարգավորվող բացառություններ

class TooManyBooksError(Exception):  # Define a new exception class
    pass

def checkout_books(user, num_books):
    if num_books > 5:  
        # Raise an exception if the user tries to check out more than 5 books
        raise TooManyBooksError('You cannot check out more than 5 books at a time.')  # Raise our custom exception
    # Otherwise, add the books to the user's account.
    user.books += num_books

try:
    checkout_books(user, 7)     # Try to check out 7 books.
except TooManyBooksError as e:  # Catch our custom exception
    print(e)                    # Print the error message.

class TooManyBooksError(Exception):  
    def __init__(self, attempted, limit=5, checked_out=0):  
        self.attempted = attempted
        self.limit = limit
        self.checked_out = checked_out
        self.message = f'You tried to check out {self.attempted} books, but the limit is {self.limit} books.'
        super().__init__(self.message)
    
    def books_to_return(self):
        return self.checked_out + self.attempted - self.limit

try:
    checkout_books(user, 7)
except TooManyBooksError as e:
    print(e)                                                   # You tried to check out 7 books, but the limit is 5 books.
    print(f'You need to return {e.books_to_return()} books.')  # You need to return 2 books.