python - 限制属性的创建/设置

Question

如何在其类/子类之外限制属性的创建？

__all__ = ["Employee","Salary","Wage"]
##################################################################################################
class Person(object):
    def __init__(self,fname,lname,gender):
        self.__setfname(fname) # "We are all adults." vs. "Name mangling."
        self.__setlname(lname)
        self.__setgender(gender)
    def __setfname(self,fname): self.__fname = fname
    def __setlname(self,lname): self.__lname = lname
    def __setgender(self,gender): self.__gender = gender
    def getname(self): return "{} {}".format(self.__fname,self.__lname)
    def getformattedname(self):
        if(self.__gender.lower() == "m"):
            return "Mr. {}".format(self.getname())
        if(self.__gender.lower() == "f"):
            return "Ms. {}".format(self.getname())
        if(self.__gender.lower() == ""):
            return "{}".format(self.getname())
class Payment(object):
    def __init__(self,amount,currency="INR"): # currency="USD"
        self.__setamount(amount)
        self.__setcurrency(currency)
    def __setamount(self,amount): self.__amount = amount
    def __setcurrency(self,currency): self.__currency = currency
    def getamount(self): return "{}".format(self.__amount)
    def getformattedamount(self): return "{} {}".format(self.getamount(),self.__currency)
##################################################################################################
##################################################################################################
class Employee(Person):
    def __init__(self,fname,lname,gender): super(Employee,self).__init__(fname,lname,gender)
    def __str__(self): return self.getformattedname()
class Salary(Payment):
    def __init__(self,amount,currency="INR"): super(Salary,self).__init__(amount,currency)
    def __str__(self): return self.getformattedamount()
class Wage(Payment):
    def __init__(self,amount,currency="INR"): super(Wage,self).__init__(amount,currency)
    def __str__(self): return self.getformattedamount()
##################################################################################################

---

我同意这个:

e1._Person__fname = "Spam"
s1._Payment__amount = "1000000000000000"

但是下面的代码创建了新的属性:

e1.fname = "New"
s1.amount = -10

---

import re
from com.example.model import Employee,Salary,Wage

def printzip(l1,l2): print(list(zip([str(e) for e in l1],[str(e) for e in l2])))

(e1,e2) = (Employee("Sandeep","Mehta","m"),Employee("Varsha","Mehta","f"))
(s1,s2) = (Salary(3000,"USD"),Salary(3000,"USD"))

printzip([e1,e2],[s1,s2])
e1.fname = "New"
s1.amount = -3000
e1._Person__fname = "Spam"
s1._Payment__amount = "3000000000000000"

for e in enumerate([e for e in dir(e1) if not (re.search(r"^__.*__$",e))]): print(e)
for e in enumerate([e for e in dir(s1) if not (re.search(r"^__.*__$",e))]): print(e)
printzip([e1],[s1])

Answer 1

不要尝试这样做。别人对你的类(class)做什么不关你的事。您应该记录哪些属性是可用的，如果有人想滥用它那是他们的问题，而不是您的问题。

“我们都是同意的成年人”是 Pythonic 哲学。