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我试图在Python中创建一个大小写和标点符号不敏感的字符串类,但在创建新实例时不调用__init__
>>> class String: def __init__(self, string): self.__string = tuple(string.split()) self.__simple = tuple(self.__simple()) def __simple(self): letter = lambda s: ''.join(filter(lambda s: 'a' <= s <= 'z', s)) return filter(bool, map(letter, map(str.lower, self.__string))) def __eq__(self, other): assert isinstance(other, String) return self.__simple == other.__simple def __getitem__(self, key): assert isinstance(key, slice) string = String() string.__string = self.__string[key] string.__simple = self.__simple[key] return string def __iter__(self): return iter(self.__string) >>> String('Hello, world!')[1:] Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> String('Hello, world!')[1:] File "<pyshell#1>", line 17, in __getitem__ string = String() TypeError: __init__() takes exactly 2 positional arguments (1 given) >>>
我该换什么?string = String(); string.__string = self.__string[key]; string.__simple = self.__simple[key]
如何用切片初始化新对象?
我找到的是:
def __init__(self, string=None): if string is None: self.__string = self.__simple = () else: self.__string = tuple(string.split()) self.__simple = tuple(self.__simple())
class String(object): ... bare_s = String.__new__(String)
这个通常用于classmethod
S作为“替代构造函数”工作,因此您通常会看到它以如下方式使用:
@classmethod def makeit(cls): self = cls.__new__(cls) # etc etc, then return self