Data encapsulation and private attributes
Like javain the general use privateand protectedto implement private methods and protected methods in the class.
I have chapter04written a class_method.pyfile in the folder, and a Dateclass is defined in the file . DateSee this blog for specific classes
Then we import the Dateclass
from chapter04.class_method import Date
class User:
def __init__(self):
self.brithday = birthday
def get_age(self):
#返回年龄
return 2018 - self.birthday.year
if __name__ = "__main__":
user = User(Date(1990,2,1))
print(user.get_age()) # 28 2018-1990
print(user.birthday) # 1990/2/1 可以获取到用户的birthday
UserThe parameter passed in the initialization of the class is a date of birth, but if we want to hide the object when getting someone's age birthday, that is , it cannot be directly accessed birthday, hide it.
pythonUse double underline to encapsulate private attributes.
class User:
def __init__(self):
self.__brithday = birthday
def get_age(self):
#返回年龄
return 2018 - self.__birthday.year
if __name__ = "__main__":
user = User(Date(1990,2,1))
print(user.get_age()) # 28
print(user.__birthday) # ‘User’ object has no attribute ‘__birthday’
Private properties cannot be obtained through 实例.私有属性or through subclasses, but they can still be used in public methods in the class, that is, the print(user.get_age())result is 28.
Adding a double underscore in front of a function can also hide the function, but in theory, the double underscore does not solve the absolute privacy of private properties from the language level, but adds a little trick. Will __birthdaybecome _User__birthdaysuch a structured method.
_User__birthdayWhich Userrepresents the current class, if it is another class, change to another class name, which can also alleviate the conflict of the same attribute name between different classes.
print(user._User__birthday) # 1990/2/1
#这样就能访问到了