如何解决如何创建仅继承特定属性的对象的别名
我正在用python编写程序,用户可以在其中添加名称和数字到列表中。 我将条目保存在具有2个属性的类中,并将该类的实例另存为列表中的对象:
class NewEntry:
def __init__(self):
self.name = ""
self.number = ""
entry = NewEntry()
entry.name = userinput[1]
entry.number = userinput[2]
entrylist.append(entry)
我现在正尝试添加一个称为别名的函数,该函数将以新名称保存一个条目。别名应以这样一种方式连接到原始条目,即更改别名之一的数量会将每个相应别名的数量更改为相同的值。 这是我尝试执行的代码:
for key in entrylist:
if key.name == userinput[1]:
entry = key
entry.name = userinput[2]
entrylist.append(entry)
这无法正常工作。创建新别名时,它还会更改key的.name,我试图仅从中继承数字属性。
我还尝试了以下方法:
for key in entrylist:
if key.name == userinput[1]:
entry = NewEntry()
entry.name = userinput[2]
entry.number = key.number
entrylist.append(entry)
TL; DR: 我希望能够创建一个对象的副本,其中所有别名中的.number-attribute均相同。我希望所有这些对象的名称都不同,但数量保持不变。别名之一的数量更改也会影响其他别名。
解决方法
您可以通过添加alias_of
属性来链接它们,以表示名称的别名。
如果将其与property
属性的number
配对,则可以控制实际设置的对象。
class NewEntry:
# I added the attributes as constructor
# arguments since you're setting them anyway
def __init__(self,name='',number=None,alias_of=None):
self.name = name
# since we want self.number to be a property
# it is common practice to use a _ to signify
# that an attribute is private
self._number = number
# here alias will refer to the instance it's
# an alias of. It defaults to None
# or not an alias
self.alias_of = alias_of
# giving a method a @property decorator
# makes it get the attribute from here
# That way you control which number it's getting
@property
def number(self):
if self.alias_of:
return self.alias_of.number
else:
return self._number
# The same is true if you give it a setter
# method. It controls which instances number
# that you set
@number.setter
def number(self,value):
if self.alias_of:
self.alias_of.number = value
else:
self._number = value
entry = NewEntry('my name',number=1)
entry2 = NewEntry('my name 2',number=2)
# here we say that entry3 is an alias of entry
entry3 = NewEntry('my other name',alias_of=entry)
print(entry.number)
print(entry2.number)
# and here entry3 is actually setting entry
# 1's number attribute
entry3.number = 3
print(entry.number)
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