Question

要实现可订阅对象很简单，只需在此对象的类定义中实现__getitem__即可但是现在我想实现一个可订阅的类。例如，我想实现此代码：

class Fruit(object):
    Apple = 0
    Pear = 1
    Banana = 2
    #________________________________ 
    #/ Some other definitions,         \
    #\ make class 'Fruit' subscriptable. /
    # -------------------------------- 
    #        \   ^__^
    #         \  (oo)\_______
    #            (__)\       )\/\
    #                ||----w |
    #                ||     ||

print Fruit['Apple'], Fruit['Banana']
#Output: 0 2

我知道getattr可以做同样的事情，但我觉得下标访问更优雅。

Answer 1

似乎通过更改元类来工作。对于Python 2：

class GetAttr(type):
    def __getitem__(cls, x):
        return getattr(cls, x)

class Fruit(object):
    __metaclass__ = GetAttr

    Apple = 0
    Pear = 1
    Banana = 2

print Fruit['Apple'], Fruit['Banana']
# output: 0 2

在Python 3上，您应该直接使用Enum：

import enum

class Fruit(enum.Enum):
    Apple = 0
    Pear = 1
    Banana = 2

print(Fruit['Apple'], Fruit['Banana'])
# Output: Fruit.Apple, Fruit.Banana
print(Fruit['Apple'].value, Fruit['Banana'].value)
# Output: 0 2

Answer 2

在课堂上添加以下内容：

class Fruit(object):
     def __init__(self):
         self.Fruits = {"Apple": 0, "Pear": 1, "Banana": 2}
     def __getitem__(self, item):
         return self.Fruits[item]

Answer 3

如果要对所有类属性执行此操作，只需扩展@Luis Kleinwort的答案，


>>>fruitsdict = {'apple':0, 'banana':1}

>>>class Fruits(object):
    def __init__(self, args):
        for k in args:
            setattr(self, k, args[k])

    def __getitem__(self, item):
         return getattr(self, item)

>>>fruits = Fruits(fruitsdict)

>>>print(fruits.apple)
0
>>>print(fruits['apple'])
0

如何在Python中实现可订阅类（可订阅类，而不是可订阅对象）？

3 个答案: