__Python 3中的元类
在Python2.7中,这段代码可以很好地工作,__Python 3中的元类,python,metaclass,Python,Metaclass,在Python2.7中,这段代码可以很好地工作,元表中的\uuu getattr\uuuu 我会跑的。但在Python3中,它不起作用 class MetaTable(type): def __getattr__(cls, key): temp = key.split("__") name = temp[0] alias = None if len(temp) > 1: alias = tem
元表中的\uuu getattr\uuuu
我会跑的。但在Python3中,它不起作用
class MetaTable(type):
def __getattr__(cls, key):
temp = key.split("__")
name = temp[0]
alias = None
if len(temp) > 1:
alias = temp[1]
return cls(name, alias)
class Table(object):
__metaclass__ = MetaTable
def __init__(self, name, alias=None):
self._name = name
self._alias = alias
d = Table
d.student__s
但在Python 3.5中,我得到了一个属性错误:
Traceback (most recent call last):
File "/Users/wyx/project/python3/sql/dd.py", line 31, in <module>
d.student__s
AttributeError: type object 'Table' has no attribute 'student__s'
回溯(最近一次呼叫最后一次):
文件“/Users/wyx/project/python3/sql/dd.py”,第31行,在
d、 学生
AttributeError:类型对象“Table”没有属性“student\u”
Python3,\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
不再被选中
在类签名中使用元类=…
:
演示:
类元表(类型):
... def_u_getattr__(cls,键):
... temp=键拆分(“\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
... name=temp[0]
... 别名=无
... 如果透镜(温度)>1:
... 别名=温度[1]
... 返回cls(名称、别名)
...
>>>类表(对象,元类=元表):
... def uuu init uuuu(self,name,alias=None):
... self.\u name=name
... self.\u别名=别名
...
>>>d=表格
>>>博士生
如果需要在代码库中同时支持Python 2和Python 3,可以使用或来指定元类。谢谢。它让我最喜欢的插件系统在Python3中工作。
可以保留现有的_元类_;语法
@CodeFarmer:是的,但它不再起任何作用了。
class Table(object, metaclass=MetaTable):
>>> class MetaTable(type):
... def __getattr__(cls, key):
... temp = key.split("__")
... name = temp[0]
... alias = None
... if len(temp) > 1:
... alias = temp[1]
... return cls(name, alias)
...
>>> class Table(object, metaclass=MetaTable):
... def __init__(self, name, alias=None):
... self._name = name
... self._alias = alias
...
>>> d = Table
>>> d.student__s
<__main__.Table object at 0x10d7b56a0>