Question

您好，我指的是以下链接 How do I manipulate bits in Python? 如果我执行最后一个响应的答案代码，我会得到以下错误。以下是快速参考的代码段

import math
class BitVector:
      def __init__(self,val):
         self._val = val

      def __setslice__(self,highIndx,lowIndx,newVal):
         assert math.ceil(math.log(newVal)/math.log(2)) <= (highIndx-lowIndx+1)

         # clear out bit slice
         clean_mask = (2**(highIndx+1)-1)^(2**(lowIndx)-1)

         self._val = self._val ^ (self._val & clean_mask)
         # set new value
         self._val = self._val | (newVal<<lowIndx)
     def __getslice__(self,highIndx,lowIndx):
         return (self._val>>lowIndx)&(2L**(highIndx-lowIndx+1)-1) ## Error in the code I think it is not 2L.
b = BitVector(0)
b[3:0]   = 0xD
b[7:4]   = 0xE
b[11:8]  = 0xA
b[15:12] = 0xD

for i in xrange(0,16,4):
    print '%X'%b[i+3:i]

在上面的代码中修复错误（2L更改为2 **）后，我得到以下错误

当我尝试执行上面的代码时，我得到以下错误Traceback（最近一次调用last）：File＆＃34; BitVector.py＆＃34;，第20行，b [3：0] = 0xD TypeError：＆＃39;位向量＆＃39;对象不支持项目分配

Answer 1

自Python2.6和removed in Python3.5以来，

__setslice__和__getslice__已被弃用。请改用__setitem__和__getitem__：

import math

class BitVector:
    """
    http://stackoverflow.com/a/150411/190597 (Ross Rogers)
    Updated for Python3
    """
    def __init__(self, val):
        self._val = val

    def __setitem__(self, item, newVal):
        highIndx, lowIndx = item.start, item.stop
        assert math.ceil(
            math.log(newVal) / math.log(2)) <= (highIndx - lowIndx + 1)

        # clear out bit slice
        clean_mask = (2 ** (highIndx + 1) - 1) ^ (2 ** (lowIndx) - 1)

        self._val = self._val ^ (self._val & clean_mask)
        # set new value
        self._val = self._val | (newVal << lowIndx)

    def __getitem__(self, item):
        highIndx, lowIndx = item.start, item.stop
        return (self._val >> lowIndx) & (2 ** (highIndx - lowIndx + 1) - 1)

b = BitVector(0)
b[3:0] = 0xD
b[7:4] = 0xE
b[11:8] = 0xA
b[15:12] = 0xD

for i in range(0, 16, 4):
    print('%X' % b[i + 3:i])

打印

D
E
A
D

位操纵Python的澄清

1 个答案: