无法访问从父 class 继承的属性

Question

class People:
    #parrent to both Employee and Costumer classes
    def __init__(self, id, name, ssn): #define class People
                                       #self used to accesses attributes and methodes in class
    #set insatance variable
        self.__id = id
        self.__name = name
        self.__ssn = ssn

class Employee(People):
    #Child of Class People
    def __init__(self, id, name, ssn, password):
        People.__init__(self, id, name,ssn)
        self.__password = password

    def __str__(self):
        return f"ID :{self.__id}\nName :{self.__name}\nSSN :{self.__ssn}\nPassword :{self.__password}"

Answer 1

Naming variable with double underscore prefix (eg __somename ) triggers python "name mangling". This is intended to prevent name collision, and as a result, Python requires a special attribute name to access: _ClassName__somename instead of __somename .

For example:

class Person():
   def __init__(self, name):
        self.__name = name

>>> Person("x").__name
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Person' object has no attribute '__name'
>>> Person("x")._Person__name
'x'

To fix this you should either use the "mangled" name to access, or rename your variables to remove the double underscore.

For more details see this detailed stackoverflow post on this topic .