8, the package Hide
Python in hidden mode : the name starts with a double underscore
class Item:
def __init__(self):
self.__name = '电子产品'
im = Item()
print(im.__name)
AttributeError: 'Item' object has no attribute '__name'
Analysis : After the hides can not be directly accessed.
Hidden nature : Python will "secretly" member name change starts with a double underline, underline and add a single class name before the member name (can be called "hidden" members in this way, is not recommended).
print(im._Item__name)
电子产品
Example:
class User:
# 构造方法中检查赋值
def __init__(self, name='Noname', passwd='default'):
if isinstance(name, str) and 4<=len(name)<=8:
self.__name = name
else:
print('用户名无效，未成功设置')
self.__name = 'Noname'
if isinstance(passwd, str) and 6<=len(passwd)<=12:
self.__passwd = passwd
else:
print('密码无效，未成功设置')
self.__passwd = 'default'
def getname(self):
return self.__name
# 检查用户名赋值，避免传入无效的值
def setname(self, name):
if isinstance(name, str) and 4<=len(name)<=8:
self.__name = name
else:
print('用户名无效，未成功设置')
name = property(fget=getname, fset=setname)
def getpasswd(self):
return self.__passwd
# 检查密码赋值，避免传入无效的值
def setpasswd(self, passwd):
if isinstance(passwd, str) and 6<=len(passwd)<=12:
self.__passwd = passwd
else:
print('密码无效，未成功设置')
passwd = property(fget=getpasswd, fset=setpasswd)
u = User('py','1')
print('-'*30)
print(u.name, u.passwd)
用户名无效，未成功设置
密码无效，未成功设置
------------------------------
Noname default
u = User('python','123456')
print('-'*30)
print(u.name, u.passwd)
------------------------------
python 123456
u.name = 'j'
print('-'*30)
print(u.name)
用户名无效，未成功设置
------------------------------
python
u.name = 'java'
print('-'*30)
print(u.name)
------------------------------
java
Analysis : If the package is not used, u.name and u.passwd may be assigned to any use of the package contents, u.name only be set to 4 to 8 bit string, u.passwd only be set to 6 to 12 String.