Python 访问限制 private public的详细介绍

>b.score
99
>b.score = 59
>b.score
59

class Student(object):   
  def __init__(self, name, score):     
    self.__name = name     
    self.__score = score   
    
  def print_score(self):     
    print('%s: %s' % (self.__name, self.__score))

> bart = Student('Bart Simpson', 98) 
> bart.__name # 私有变量：不能被外部访问
Traceback (most recent call last):  
File "<stdin>", line 1, in <module> 
AttributeError: 'Student' object has no attribute '__name'

class Student(object):
  ...
  def get_name(self):     
    return self.__name   
  def get_score(self):     
    return self.__score 

...
def set_score(self, score): 
  # 避免传入无效参数 
  if 0 <= score <= 100: 
    self.__score = score 
  else:       
    raise ValueError('bad score') 

> bart = Student('Bart Simpson', 98)
> bart.get_name() 
'Bart Simpson' 
> bart.__name = 'New Name' # 给bart新增的__name变量 
> bart.__name        # ！与class内部的__name变量不是一个变量！
'New Name' 
> bart.get_name()      # get_name()内部返回self.__name (_Student__name)
'Bart Simpson'  

def _private_1 (name):
  return 'hello,%s ' % name
def _private_2 (name):
  return 'hi , %s ' % name
def greeting(name):
  if len(name) > 3:
    return _private_1 (name)
  else:
    return _private_2 (name)

class Student(object):   
  def __init__(self, name, score):     
    self.__name = name     
    self.__score = score   
    
  def print_score(self):     
    print('%s: %s' % (self.__name, self.__score))
  
  def get_name(self):     
    return self.__name   
  
  def get_score(self):     
    return self.__score
    
  def set_score(self, score): 
    # 避免传入无效参数 
    if 0 <= score <= 100: 
      self.__score = score 
    else:       
      raise ValueError('bad score')  
      
  def _private_1 (name):
    return 'hello,%s ' % name
  def _private_2 (name):
    return 'hi , %s ' % name
  def greeting(name):
    if len(name) > 3:
      return _private_1 (name)
    else:
      return _private_2 (name)