添加屬性類列表與特定屬性

讓我們來設置場景！

說我有一類人有幾個基本屬性：

class Person(object): 
    def __init__(self, name=None, gender=None, single=None): 
     self.name=name 
     self.gender=gender 
     self.single=single

我創建一個名爲約會列表類，將容納所有Person對象

class Dating(object): 
    def __init__(self): 
     self.members=[] 

My_People=Dating() 

My_People.members.append(Person("Jack","Male",False)) 
My_People.members.append(Person("Jill","Female",True)) 
My_People.members.append(Person("George","Male",True)) 
My_People.members.append(Person("Sandy","Female",False))

對，所以問題是什麼？

是否有可能分配到列表類的屬性，通過建立某種類似屬性的訪問My_People列表的單一成員：

My_People.members.singles

所以，這將返回Person對象的列表有單個==真屬性？

感謝您的幫助。（順便說一下，我有使用Python很少以往的經驗）

來源

2014-06-20 user1083734

結束調用的'__init__'方法，它以這種方式工作沒有你的幫助） – alexvassel

已編輯的問題。現在好多了？ – user1083734

是的，當然！） – alexvassel

要添加這樣的屬性，你就必須子列表類型：

class FilterableList(list): 
    def __getattr__(self, name): 
     # assume non-existing attributes are boolean filters 
     return [elem for elem in self if getattr(elem, name)]

注意，這還不是全部那靈活;只有True值可以通過這種方式找到。你可以給屬性名更多的含義，但通常你會想這樣做的Dating類不管怎樣，使用方法更意味深長地過濾數據。

演示：

所有的

>>> class Person(object): 
...  def __init__(self, name, gender, single): 
...   self.name=name 
...   self.gender=gender 
...   self.single=single 
...  def __repr__(self): 
...   return 'Person({name!r}, {gender!r}, {single!r})'.format(**vars(self)) 
... 
>>> class FilterableList(list): 
...  def __getattr__(self, name): 
...   # assume non-existing attributes are boolean filters 
...   return [elem for elem in self if getattr(elem, name)] 
... 
>>> members = FilterableList([Person("Jack","Male",False), Person("Jill","Female",True), Person("George","Male",True), Person("Sandy","Female",False)]) 
>>> members 
[Person('Jack', 'Male', False), Person('Jill', 'Female', True), Person('George', 'Male', True), Person('Sandy', 'Female', False)] 
>>> members.single 
[Person('Jill', 'Female', True), Person('George', 'Male', True)]

來源

2014-06-20 11:47:36

感謝這一點，這正是我需要的，我喜歡解決方案的靈活性。此外，我從來沒有使用__repr__，它真的會派上用場！ – user1083734

首先，你並不需要調用__init__()在My_People例如，Python做自動。

對於這個問題，你可以從list子類，並添加singles屬性是這樣的：

class Person(object): 
    def __init__(self, name=None, gender=None, single=None): 
     self.name=name 
     self.gender=gender 
     self.single=single 

class Dating(list): 
    @property 
    def singles(self): 
     return [person for person in self if person.single ] 

My_People=Dating() 

My_People.append(Person("Jack","Male",False)) 
My_People.append(Person("Jill","Female",True)) 
My_People.append(Person("George","Male",True)) 
My_People.append(Person("Sandy","Female",False)) 

print My_People.singles

來源

2014-06-20 11:49:26 Fabian

太棒了，我明白這一點。因此，每次要訪問My_People.singles時都必須遍歷My_People列表，並且沒有直接用單一== True屬性調用這些對象的方法。 – user1083734

我喜歡從列表中繼承的建議，非常方便 – user1083734

@ user1083734您當然可以保存''.singles''返回的結果，以避免在每次訪問時遍歷列表。 – Fabian

怎麼樣：

class Attribute(list): 
    def __getattr__(self, attr): 
     if attr == 'single': 
      return [person for person in self if person.single] 
     raise AttributeError() 

class Person(object): 
    def __init__(self, name=None, gender=None, single=None): 
     self.name = name 
     self.gender = gender 
     self.single = single 

    def __repr__(self): 
     return 'Person({person.name}, {person.gender}, {person.single})'.format(person=self) 


class Dating(object): 
    members = Attribute() 


My_People = Dating() 

My_People.members.append(Person("Jack", "Male", False)) 
My_People.members.append(Person("Jill", "Female", True)) 
My_People.members.append(Person("George", "Male", True)) 
My_People.members.append(Person("Sandy", "Female", False)) 

>>> print My_People.members.single 
[Person(Jill, Female, True), Person(George, Male, True)] 
>>> print My_People.members 
[Person(Jack, Male, False), Person(Jill, Female, True), Person(George, Male, True), Person(Sandy, Female, False)]

來源

2014-06-20 12:04:22 alexvassel

如果你不依賴於My_People.members.singles語法，你可以做得更簡單：

class Dating(object): 

    def __init__(self): 
     self.members = [] 

    @property 
    def single_members(self): 
     return [m for m in members if m.single]

現在你訪問列表具有：

My_People.single_members

來源

2014-06-20 12:41:41 jonrsharpe

添加屬性類列表與特定屬性

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