处理这个问题的一个很酷的方法是创建一个通用的BitMask：
import string
import itertools
class BitMask(object):
STR_TOKENS = string.ascii_letters
STR_EMPTY = '_'
STR_FULL = False
def __init__(
self,
value=None,
ignore=True):
if isinstance(value, str):
self.value = self.from_tokens(value, self.STR_TOKENS, ignore)
else:
self.value = value
def __repr__(self):
return bin(self.value)
def __iter__(self):
value = self.value
while value:
yield value & 1
value >>= 1
def to_tokens(self, tokens, empty, full):
if full:
return [
token if value else empty
for token, value in
itertools.zip_longest(tokens, self, fillvalue=False)]
else:
return [
token for token, value in zip(tokens, self) if value]
def __str__(self):
return ''.join(
self.to_tokens(self.STR_TOKENS, self.STR_EMPTY, self.STR_FULL))
def from_tokens(self, seq, tokens, ignore):
if tokens is None:
tokens = self.STR_TOKENS
valid_tokens = set(tokens)
value = 0
for i, item in enumerate(seq):
if item in valid_tokens:
value |= 1 << tokens.index(item)
elif not ignore:
raise ValueError(f'Invalid input `{item}` at index: {i}.')
return value
def __add__(self, other):
self.value |= other.value
return self
def __mul__(self, other):
self.value &= other.value
return self
def __eq__(self, other):
return type(self) == type(other) and self.value == other.value
您可以根据需要对其进行子类化，例如：
class MyBitMask(BitMask):
STR_TOKENS = string.ascii_uppercase
def __init__(self, value=None, ignore=False):
super().__init__(value, ignore)
print(str(MyBitMask(5)))
# AC
print(str(MyBitMask(15)))
# ABCD
还有：
repr(MyBitMask('AC'))
# 0b101
MyBitMask('AC') == MyBitMask(5)
# True
MyBitMask('AC') == BitMask(5) # NOT THE SAME BITMASK CLASS!
# False
在时间上，冷静会消耗速度，即（与其他答案中的方法相比）：
def convert(value, tokens=string.ascii_uppercase):
output = ''
i = 0
while value:
if value & 1:
output += tokens[i]
i += 1
value >>= 1
return output
def convert2(value, tokens=string.ascii_uppercase):
return ''.join(tokens[i] for i, c in enumerate(bin(value)[:1:-1]) if c == '1')
def convert3(value, tokens=string.ascii_uppercase):
result = []
i = 0
while value:
if value & 1:
result.append(tokens[i])
i += 1
value >>= 1
return ''.join(result)
def convert4(value, tokens=string.ascii_uppercase):
return ''.join(tokens[pos] for pos in range(value.bit_length()) if value & (1 << pos))
def convert5(value, tokens=string.ascii_uppercase):
return ''.join(c for b, c in zip(reversed('{:b}'.format(value)), tokens) if b == '1')
print([convert(i) for i in range(16)])
print([convert2(i) for i in range(16)])
print([convert3(i) for i in range(16)])
print([convert4(i) for i in range(16)])
print([convert5(i) for i in range(16)])
print([str(MyBitMask(i)) for i in range(16)])
# ['', 'A', 'B', 'AB', 'C', 'AC', 'BC', 'ABC', 'D', 'AD', 'BD', 'ABD', 'CD', 'ACD', 'BCD', 'ABCD']
%timeit [convert(i) for i in range(1024)]
%timeit [convert2(i) for i in range(1024)]
%timeit [convert3(i) for i in range(1024)]
%timeit [convert4(i) for i in range(1024)]
%timeit [convert5(i) for i in range(1024)]
%timeit [str(MyBitMask(i)) for i in range(1024)]
1.8 ms ± 5.45 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
2.11 ms ± 83.2 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
2.29 ms ± 331 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
3.42 ms ± 1.03 ms per loop (mean ± std. dev. of 7 runs, 100 loops each)
2.24 ms ± 103 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
4.48 ms ± 151 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)