使用许多@properties 扩展 Python 命名元组? [英] extend Python namedtuple with many @properties?

问题描述

如何使用许多额外的@properties 扩展或子类化命名元组?
对于少数人，可以只写下面的文字；但有很多，所以我正在寻找发电机或财产工厂.一种方法是从 _fields 生成文本并执行它；另一个是在运行时具有相同效果的 add_fields.
(我的@props 是获取行和字段在分散在几个表中的数据库中，所以 rec.pname 是 persontable[rec.personid].pname;但namedtuples-with-smart-fields 也有其他用途.)

""" 用许多@properties 扩展namedtuple ? """从集合导入命名元组Person = namedtuple( "Person", "pname paddr" ) # ...人物表 = [人(史密斯"，纽约")，人(琼斯"，IL")]class Top( namedtuple( "Top_", "topid amount personid" )):"@财产.person ->人物表[人物ID].pname ->人名..."""__slots__ = ()@财产定义人(自己):返回个人表[self.personid]# def add_fields( self, Top.person, Person._fields ) 和这些效果一样吗?@财产def pname(self):返回 self.person.pname@财产def paddr(自我):返回 self.person.paddr# ... 还有很多rec = 顶部( 0, 42, 1 )打印 rec.person、rec.pname、rec.paddr

解决方案

问题的答案

<块引用>

命名元组如何扩展或使用额外的 @properties 子类化?

就是:完全按照您的方式进行！你遇到了什么错误?要查看更简单的案例，

<预><代码>>>>类 x(collections.namedtuple('y', 'a b c')):... @财产... def d(self): 返回 23...>>>a=x(1, 2, 3)>>>广告23>>>

How can namedtuples be extended or subclassed with many additional @properties ?
For a few, one can just write the text below; but there are many, so I'm looking for a generator or property factory. One way would be to generate text from _fields and exec it; another would be an add_fields with the same effect at runtime.
(My @props are to get rows and fields in a database scattered across several tables, so that rec.pname is persontable[rec.personid].pname; but namedtuples-with-smart-fields would have other uses too.)

""" extend namedtuple with many @properties ? """
from collections import namedtuple

Person = namedtuple( "Person", "pname paddr" )  # ...
persontable = [
    Person( "Smith", "NY" ),
    Person( "Jones", "IL" )
    ]

class Top( namedtuple( "Top_", "topid amount personid" )):
    """ @property 
        .person -> persontable[personid]
        .pname -> person.pname ...
    """
    __slots__ = ()
    @property
    def person(self):
        return persontable[self.personid]

    # def add_fields( self, Top.person, Person._fields ) with the same effect as these ?
    @property
    def pname(self):
        return self.person.pname
    @property
    def paddr(self):
        return self.person.paddr
    # ... many more

rec = Top( 0, 42, 1 )
print rec.person, rec.pname, rec.paddr

解决方案

The answer to your question

How can namedtuples be extended or subclassed with additional @properties ?

is: exactly the way you're doing it! What error are you getting? To see a simpler case,

>>> class x(collections.namedtuple('y', 'a b c')):
...   @property
...   def d(self): return 23
... 
>>> a=x(1, 2, 3)
>>> a.d
23
>>> 

这篇关于使用许多@properties 扩展 Python 命名元组?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！