可以包裹在发电机表达的范围内,将所述移位和模上飞:
def shifted_range(rangeob, shift):
size, shift = rangeob.stop, shift * rangeob.step
return ((i + shift) % size for i in rangeob)
演示:
>>> def shifted_range(rangeob, shift):
... size, shift = rangeob.stop, shift * rangeobj.step
... return ((i + shift) % size for i in rangeob)
...
>>> range_10 = range(10)
>>> list(shifted_range(range_10, 3))
[3, 4, 5, 6, 7, 8, 9, 0, 1, 2]
>>> list(shifted_range(range_10, 7))
[7, 8, 9, 0, 1, 2, 3, 4, 5, 6]
>>> range_10_2 = range(0, 10, 2)
>>> list(shifted_range(range_10_2, 4))
[8, 0, 2, 4, 6]
你能做出这样一个包装对象,以及:
class RangeShift:
def __init__(self, rangeob, shift):
self._range = rangeob
self.shift = shift
@property
def start(self):
r = self._range
return (r.start + self.shift * r.step) % r.stop
@property
def stop(self):
r = self._range
return (r.stop + self.shift * r.step) % r.stop
def index(self, value):
idx = self._range.index(value)
return (idx - self.shift) % len(self._range)
def __getattr__(self, attr):
return getattr(self._range, attr)
def __getitem__(self, index):
r = self._range
return (r[index] + self.shift * r.step) % r.stop
def __len__(self):
return len(self._range)
def __iter__(self):
size, shift = self._range.stop, self.shift * self._range.step
return ((i + shift) % size for i in self._range)
这将表现就像原来的范围,但应用转移到生产的所有值。它甚至可以让你改变班次!
演示:
>>> range_10 = range(10)
>>> shifted = RangeShift(range_10, 7)
>>> len(shifted)
10
>>> shifted.start
7
>>> shifted.stop
7
>>> shifted.step
1
>>> shifted[3]
0
>>> shifted[8]
5
>>> list(shifted)
[7, 8, 9, 0, 1, 2, 3, 4, 5, 6]
>>> shifted.shift = 3
>>> list(shifted)
[3, 4, 5, 6, 7, 8, 9, 0, 1, 2]
>>> range_10_2 = range(0, 10, 2)
>>> shifted_10_2 = RangeShift(range_10_2, 4)
>>> list(shifted_10_2)
[8, 0, 2, 4, 6]
此包装现在支持
绝招:倒车变速范围:
>>> list(reversed(shifted))
[2, 1, 0, 9, 8, 7, 6, 5, 4, 3]
>>> list(reversed(shifted_10_2))
[6, 4, 2, 0, 8]
感谢这个详细的解答。 (我想至少有一封包含感谢的评论是允许的,而不会被视为垃圾邮件):P – Nimi 2014-10-29 15:27:34