Question

我有一个类，我在其中存储slice对象，因为实际的切片发生在应用程序的后续部分。但是，在这个函数的__repr__中，我想要打印一些看起来像你自己写的东西。

class DelaySlice(object):
    def __init__(self, obj, slice):
        self.obj = obj
        self.slice = slice
    def __repr__(self):
        return "%s[%s]" % (self.obj, self.slice)

class OtherObject(object):
    def __repr__(self):
        return "other_object_instance"
    def __getitem__(self, slice):
        return DelaySlice(self, slice)

有了这个，print(OtherObject()[:2]打印other_object_instance[slice(None, 2, None)]。我希望它能打印other_object_instance[:2]。

我应该如何更改DelaySlice.__repr__以实现我想要的目标？

Answer 1

以下是针对明显情况执行此操作的代码段。

def __repr__(self):
    sl_start = "" if self.slice.start is None else str(self.slice.start)
    sl_stop = "" if self.slice.stop is None else str(self.slice.stop)
    if self.slice.step is None:
        sl_str = "%s:%s" % (sl_start, sl_stop)
    else:
        sl_str = "%s:%s:%s" % (sl_start, sl_stop, self.slice.step)
    return "%s[%s]" % (self.obj, sl_str)

如果您将其用作DelaySlice.__repr__，则会按预期打印

>>> OtherObject()[:2]
other_object_instance[:2]
>>> OtherObject()[1:2]
other_object_instance[1:2]
>>> OtherObject()[1:]
other_object_instance[1:]
>>> OtherObject()[1::4]
other_object_instance[1::4]

如何将切片对象转换为可以放在括号中的字符串？

1 个答案: