Python seter nieruchomość zdobienia z listy

Question

globalList = [] 
class MyList: 
    def __init__(self): 
     self._myList = [1, 2, 3] 

    @property 
    def myList(self): 
     return self._myList + globalList 
    @myList.setter 
    def myList(self, val): 
     self._myList = val 

mL1 = MyList() 
print("myList: ", mL1.myList) 
mL1.myList.append(4) 
print("after appending a 4, myList: ", mL1.myList) 
mL1.myList.extend([5,6,"eight","IX"]) 
print("after extend, myList: ", mL1.myList) 

Wynik:

myList: [1, 2, 3] 
after appending a 4, myList: [1, 2, 3] 
after extend, myList: [1, 2, 3] 

Problem jestem stoi to, że mL1.myList.append (4) i mL1.myList.extend ([5,6 ", osiem "," IX "]) nie modyfikuj atrybutu _myList w obiekcie mL1. Jak mogę zrobić, aby rozwiązać problem?

Answer 1

I zdefiniować append() metoda i sposób rozszerzenia() dla obiekt klasy. Odpowiednio dołącza do członka myList i rozszerza listę myList.

global globalList 
globalList = [] 
class MyList(): 
    def __init__(self): 
     self._myList = [1, 2, 3] 

    @property 
    def myList(self): 
     return self._myList + globalList 
    @myList.setter 
    def myList(self, val): 
     self._myList = val 

    def append(self, val): 
     self.myList = self.myList + [val] 
     return self.myList 

    def extend(self, val): 
     return self.myList.extend(val) 


mL1 = MyList() 
print("myList: ", mL1.myList) 
mL1.append(4) 
print("after appending a 4, myList: ", mL1.myList) 
mL1.myList.extend([5,6,"eight","IX"]) 
print("after extend, myList: ", mL1.myList) 

wynik jest

>>> 
('myList: ', [1, 2, 3]) 
('after appending a 4, myList: ', [1, 2, 3, 4]) 
('after extend, myList: ', [1, 2, 3, 4, 5, 6, 'eight', 'IX']) 

Answer 2

Chciałbym podklasy list i zastąpić kilka metod:

import itertools 

class ExtendedList(list): 
    def __init__(self, other=None): 
     self.other = other or [] 

    def __len__(self): 
     return list.__len__(self) + len(self.other) 

    def __iter__(self): 
     return itertools.chain(list.__iter__(self), iter(self.other)) 

    def __getitem__(self, index): 
     l = list.__len__(self) 

     if index > l: 
      return self.other[index - l] 
     else: 
      return list.__getitem__(self, index) 

Należy pracować z niemal wszystko:

In [9]: x = ExtendedList([1, 2, 3]) 

In [10]: x 
Out[10]: [1, 2, 3] 

In [11]: x.append(9) 

In [12]: x 
Out[12]: [9, 1, 2, 3] 

In [13]: x.extend([19, 20]) 

In [14]: x 
Out[14]: [9, 19, 20, 1, 2, 3] 

In [15]: sum(x) 
Out[15]: 54