Question

我是Python的新手，我刚刚在编程教科书中找到了OOP章节。

教科书没有解释property()的工作原理。

property()如何知道将名称更改为new_name而不是new_name + "lololol"？

我创建了set_name2因为我想了解property()的工作原理。但令我惊讶的是，这个名字没有改为new_name + "lololol"。

# Property Critter

class Critter(object):
    """A virtual pet"""
    def __init__(self, name):
        print "A new critter has been born!"
        self.__name = name

    def get_name(self):
        return self.__name

    def set_name(self, new_name):
        if new_name == "":
            print "A critter's name can't be an empty string."
        else:
            self.__name = new_name
            print "Name change successful."

    def set_name2(self, new_name):
        self.__name = new_name + "lololol"
        print "Name change successful (set_name2!)"

    name = property(get_name, set_name, set_name2)

    def talk(self):
        print "\nHi, I'm", self.name


# main

crit = Critter("Poochie")
crit.talk()
print "\nMy critter's name is:",
print crit.name
print "\nAttempting to change my critter's name."
crit.name = ""
print "\nAttempting to change my critter's name again."
crit.name = "Randolph"

crit.talk()

raw_input("\n\nPress enter to exit.")

Answer 1

property的第三个参数应该是删除属性的函数，而不是另一个setter函数（函数的名称没有特殊含义，只是命名它{{ 1}}并不能使它成为一个设定者。 official documentation of property很好地解释了set_something，fget和fset预期会做什么。

要了解 fdel如何在内部运作，您可以阅读Ashwini Chaudhary指出的descriptors。

以下是对代码的一些修改，以说明property行为：

property

哪个输出：

# Property Critter

class Critter(object):
    """A virtual pet"""
    def __init__(self, name):
        print "A new critter has been born!" 
        self.__name = name

    def get_name(self):
        return self.__name

    def set_name(self, new_name):
        if new_name == "":
            print "A critter's name can't be an empty string." 
        else:
            self.__name = new_name
            print "Name change successful." 

    def del_name(self):
        self.__name = "Scratchy"
        print "If you don't give me a name, I will choose one myself!" 

    name = property(get_name, set_name, del_name)

    def talk(self):
        print "\nHi, I'm", self.name 


# main

crit = Critter("Poochie")
crit.talk()
print "\nMy critter's name is:",
print crit.name 
crit.name = ""
crit.name = "Itchy"
crit.talk()
del crit.name
crit.talk()

Property（）如何知道该怎么做？

1 个答案: