0 Preface

Python Programming: from introduction to practice Chapter 9 class exercises - class User

1 description of exercises

Exercise 9-3 users

Create a class named User that contains the property first_name and last_name, and several other attributes that are usually stored in the User profile. Define a User class named describe_ Method of User (), which prints the summary of User information; Define another one named greet_ Method of User (), which sends personalized greetings to users.
Create multiple instances representing different users and call the above two methods for each instance.

Exercise 9-5 login attempts

In the User class you wrote to complete exercise 9-3, add a name called login_ Attributes of attempts. Write a program called increment_ login_ Method of attempts (), which takes the attribute login_ Add 1 to the value of attempts. Write another one called reset_ login_ Method of attempts (), which takes the attribute login_ The value of attempts is reset to 0.
Create an instance according to the User class, and then call the method increment_login_attempts() more than once. Print attribute login_ The value of attempts to confirm that it is incremented correctly; Then, call the method reset_. login_attempts() and print the attribute login again_ The value of attempts and confirm that it is reset to 0.

Exercise 9-7 administrator

Administrator is a special kind of User. Write a class called Admin that inherits the User class you wrote to complete exercises 9-3 or 9-5. Add an attribute named privileges to store a list of strings (such as "can add post", "can delete post", "can ban user", etc.). Write a program called show_privileges(), which displays the privileges of the administrator. Create an Admin instance and call this method.

Exercise 9-8 permissions

Write a class called privileges, which has only one attribute - privileges, which stores the list of strings described in exercise 9-7. Show method_ Move privileges () into this class. In the Admin class, use an instance of privileges as its property. Create an Admin instance and use the method show_privileges() to display its permissions.

Exercise 9-11 importing the Admin class

Based on the work done to complete exercises 9-8. Store the User, privileges and Admin classes in a module, create a file, create an Admin instance in it, and call the show method on it_ Privileges() to make sure everything works correctly.

2. Self programming

2.1 User.py

class User:

    def __init__(self, first_name, last_name, username, login_attempts):
        self.first_name = first_name
        self.last_name = last_name
        self.username = username
        self.login_attempts = login_attempts

    def describe_user(self):
        print(f"{self.first_name} {self.last_name}'s username is: {self.username}")

    def greet_user(self):
        print(f"Hello, {self.first_name} {self.last_name}")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0

    def show_login_attempts(self):
        print(f"Now your login attempts are: {self.login_attempts}")


class Privileges:
    def __init__(self, privileges=[]):
        self.privileges = privileges

    def show_privileges(self):
        if self.privileges:
            print("Your privileges are:")
            for privilege in self.privileges:
                print("-" + str(privilege))


class Admin(User):
    def __init__(self, first_name, last_name, username, login_attempts):
        super().__init__(first_name, last_name, username, login_attempts)
        self.privileges = Privileges()

2.2 main.py

from user import User, Admin

user1 = User("A", "B", 'Abb', 5)
user1.describe_user()
user1.greet_user()
user1.increment_login_attempts()
user1.show_login_attempts()
user1.reset_login_attempts()
user1.show_login_attempts()

user2 = User("C", "D", 'Cdd', 0)
user2.describe_user()
user2.greet_user()
user2.increment_login_attempts()
user2.show_login_attempts()

admin1 = Admin("E", "F", 'EfF', 10)
admin1.describe_user()
admin1.greet_user()
admin1.privileges.privileges = ['can add post', 'can delete post']
admin1.privileges.show_privileges()

2.3 Output

A B's username is: Abb
Hello, A B
Now your login attempts are: 6
Now your login attempts are: 0
C D's username is: Cdd
Hello, C D
Now your login attempts are: 1
E F's username is: EfF
Hello, E F
Your privileges are:
-can add post
-can delete post

3 exercise 9-11 importing Admin class reference answer

3.1 user.py

"""A collection of classes for modeling users."""

class User():
    """Represent a simple user profile."""

    def __init__(self, first_name, last_name, username, email, location):
        """Initialize the user."""
        self.first_name = first_name.title()
        self.last_name = last_name.title()
        self.username = username
        self.email = email
        self.location = location.title()
        self.login_attempts = 0

    def describe_user(self):
        """Display a summary of the user's information."""
        print("\n" + self.first_name + " " + self.last_name)
        print("  Username: " + self.username)
        print("  Email: " + self.email)
        print("  Location: " + self.location)

    def greet_user(self):
        """Display a personalized greeting to the user."""
        print("\nWelcome back, " + self.username + "!")

    def increment_login_attempts(self):
        """Increment the value of login_attempts."""
        self.login_attempts += 1

    def reset_login_attempts(self):
        """Reset login_attempts to 0."""
        self.login_attempts = 0


class Admin(User):
    """A user with administrative privileges."""

    def __init__(self, first_name, last_name, username, email, location):
        """Initialize the admin."""
        super().__init__(first_name, last_name, username, email, location)

        # Initialize an empty set of privileges.
        self.privileges = Privileges([])
    

class Privileges():
    """Stores privileges associated with an Admin account."""

    def __init__(self, privileges):
        """Initialize the privileges object."""
        self.privilege = privileges

    def show_privileges(self):
        """Display the privileges this administrator has."""
        for privilege in self.privileges:
            print("- " + privilege)

3.2 my_user.py

from user import Admin

eric = Admin('eric', 'matthes', 'e_matthes', 'e_matthes@example.com', 'alaska')
eric.describe_user()

eric_privileges = [
    'can reset passwords',
    'can moderate discussions',
    'can suspend accounts',
    ]
eric.privileges.privileges = eric_privileges

print("\nThe admin " + eric.username + " has these privileges: ")
eric.privileges.show_privileges()

3.3 Output

Eric Matthes
  Username: e_matthes
  Email: e_matthes@example.com
  Location: Alaska

The admin e_matthes has these privileges: 
- can reset passwords
- can moderate discussions
- can suspend accounts

3 conclusion

Chapter 46

Review Python and hope to learn something interesting
Solve the problems in your work

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