TypeError:+:'dict_keys'和'list'的不支持的操作数类型

Question

我正在尝试使用名为bidi的Python包.在这个包中的模块(algorithm.py)中,有一些行给出了错误,尽管它是包的一部分.

以下是这些行:

_LEAST_GREATER_ODD = lambda x: (x + 1) | 1
_LEAST_GREATER_EVEN = lambda x: (x + 2) & ~1

X2_X5_MAPPINGS = {
    'RLE': (_LEAST_GREATER_ODD, 'N'),
    'LRE': (_LEAST_GREATER_EVEN, 'N'),
    'RLO': (_LEAST_GREATER_ODD, 'R'),
    'LRO': (_LEAST_GREATER_EVEN, 'L'),
}

# Added 'B' so X6 won't execute in that case and X8 will run its course
X6_IGNORED = X2_X5_MAPPINGS.keys() + ['BN', 'PDF', 'B']
X9_REMOVED = X2_X5_MAPPINGS.keys() + ['BN', 'PDF']

如果我在Python 3中运行代码,我会收到以下错误消息:

Traceback (most recent call last):
  File "<pyshell#9>", line 1, in <module>
    from bidi.algorithm import get_display
  File "C:\Python33\lib\site-packages\python_bidi-0.3.4-py3.3.egg\bidi\algorithm.py", line 41, in <module>
    X6_IGNORED = X2_X5_MAPPINGS.keys() + ['BN', 'PDF', 'B']
TypeError: unsupported operand type(s) for +: 'dict_keys' and 'list'

虽然这是bidi包的一部分,但为什么会出现此错误？它与我的Python版本有什么关系吗？我很感激任何帮助.

Answer 1

在Python 3.x中,dict.keys返回一个字典视图:

>>> a = {1:1, 2:2}
>>> a.keys()
dict_keys([1, 2])
>>> type(a.keys())
<class 'dict_keys'>
>>>

您可以通过将这些视图放入以下内容来获得所需内容list:

X6_IGNORED = list(X2_X5_MAPPINGS.keys()) + ['BN', 'PDF', 'B']
X9_REMOVED = list(X2_X5_MAPPINGS.keys()) + ['BN', 'PDF']

实际上,你甚至.keys不再需要了,因为迭代字典会产生它的键:

X6_IGNORED = list(X2_X5_MAPPINGS) + ['BN', 'PDF', 'B']
X9_REMOVED = list(X2_X5_MAPPINGS) + ['BN', 'PDF']

Answer 2

是的,它与您的Python版本有关.在Python 2.x中,dict.keys返回字典键的列表.在Python 3.x中,它提供了键的视图对象.

您可以调用list()结果使其成为列表,或者只调用list()整个字典作为快捷方式.