python子类输出时怎么去掉none ？

Question

子类继承父类后输出老是有None返回，不知道怎么去掉，望指点。

# 9-7: 创建Admin类，继承9-5类；添加privileges属性，存储由字符串组成的列表；添加show_privileges()方法，显示管理员权限；创建实例验证。
class User(): 
  def __init__(self, first_name, last_name): 
    self.first_name = first_name
    self.last_name = last_name
    self.sex = 'man'
    self.tall = ''
    self.login_attempts = 0
  
  
  def increment_login_attempts(self): 
    self.login_attempts += 1
  
  
  def reset_login_attempts(self): 
    self.login_attempts = 0  # 
  
  
  def describe_user(self):
    if self.tall: 
      man = f'first_name: {self.first_name.title()} last_name: {self.last_name.title()} Sex: {self.sex.title()} Tall: {self.tall.upper()}'
      print(man)
    else: 
      woman = f'first_name: {self.first_name.title()}last_name: {self.last_name.title()}Sex: {self.sex.title()}'
      print(woman)
      
  def greet_user(self): 
    if self.sex == 'man': 
      print(f'Hello Mr. {self.first_name.title()} {self.last_name.title()}.\n\t Welcom to the python.')
    else: 
      print(f'Hello Mis. {self.first_name.title()} {self.last_name.title()}.\n\t Welcom to the python.')
      
"""创建新类，继承上类"""
class Admin(User): 
  """管理员权限说明"""
  def __init__(self, first_name, last_name): 
    """初始化父类属性"""
    super().__init__(first_name, last_name)
    self.privileges = []
    
    
  def show_privileges(self): 
    show = f'{self.greet_user()}\n\t You have {self.privileges}.'
    print(show)
a = Admin('liu', 'rui')
a.sex = 'woman'
a.privileges = ['can Add post', 'can delete post', 'can ban user']
a.show_privileges()

输出显示为

Hello Mis. Liu Rui.
     Welcom to the python.
None
     You have ['can Add post', 'can delete post', 'can ban user'].

不会去掉这个None。

Answer 1

这个None是greet_user(self):方法用的print()的返回值，改成return 就没了None

  def greet_user(self): 
    if self.sex == 'man': 
      return(f'Hello Mr. {self.first_name.title()} {self.last_name.title()}.\n\t Welcom to the python.')
    else: 
      return(f'Hello Mis. {self.first_name.title()} {self.last_name.title()}.\n\t Welcom to the python.')