在 Python 3 中将二进制字符串转换为 bytearray [英] Convert binary string to bytearray in Python 3
问题描述
尽管有很多相关问题,但我找不到与我的问题相符的问题.我想将二进制字符串(例如,"0110100001101001"
)更改为字节数组(相同的示例,b"hi"
).
我试过这个:
bytes([int(i) for i in "0110100001101001"])
但我得到了:
b'\x00\x01\x01\x00\x01' #...等等
在 Python 3 中执行此操作的正确方法是什么?
以下是 Patrick 提到的第一种方法的示例:将位串转换为 int 并一次取 8 位.这样做的自然方法是以相反的顺序生成字节.为了将字节恢复到正确的顺序,我在字节数组上使用扩展切片符号,步长为 -1:b[::-1]
.
def bitstring_to_bytes(s):v = int(s, 2)b = 字节数组()而 v:b.append(v & 0xff)v >>= 8返回字节(b[::-1])s = 0110100001101001"打印(bitstring_to_bytes(s))
显然,Patrick 的第二种方式更紧凑.:)
然而,在 Python 3 中有更好的方法来做到这一点:使用 int.to_bytes 方法:
def bitstring_to_bytes(s):return int(s, 2).to_bytes((len(s) + 7)//8, byteorder='big')
如果len(s)
保证是8的倍数,那么.to_bytes
的第一个参数可以简化:
return int(s, 2).to_bytes(len(s)//8, byteorder='big')
如果len(s)
不是 8 的倍数,这将引发 OverflowError
,这在某些情况下可能是可取的.>
另一种选择是使用双重否定来执行天花板划分.对于整数 a &b、使用//
n = a//b
给出整数 n 使得
n <= a/b 47//10
给出 4,并且
-47//10
给出 -5.所以
-(-47//10)
给出 5,有效地执行天花板分割.
因此在 bitstring_to_bytes
中我们可以做到:
return int(s, 2).to_bytes(-(-len(s)//8), byteorder='big')
然而,并没有多少人熟悉这种高效&紧凑的习语,所以通常认为它的可读性不如
return (s, 2).to_bytes((len(s) + 7)//8, byteorder='big')
Despite the many related questions, I can't find any that match my problem. I'd like to change a binary string (for example, "0110100001101001"
) into a byte array (same example, b"hi"
).
I tried this:
bytes([int(i) for i in "0110100001101001"])
but I got:
b'\x00\x01\x01\x00\x01' #... and so on
What's the correct way to do this in Python 3?
Here's an example of doing it the first way that Patrick mentioned: convert the bitstring to an int and take 8 bits at a time. The natural way to do that generates the bytes in reverse order. To get the bytes back into the proper order I use extended slice notation on the bytearray with a step of -1: b[::-1]
.
def bitstring_to_bytes(s):
v = int(s, 2)
b = bytearray()
while v:
b.append(v & 0xff)
v >>= 8
return bytes(b[::-1])
s = "0110100001101001"
print(bitstring_to_bytes(s))
Clearly, Patrick's second way is more compact. :)
However, there's a better way to do this in Python 3: use the int.to_bytes method:
def bitstring_to_bytes(s):
return int(s, 2).to_bytes((len(s) + 7) // 8, byteorder='big')
If len(s)
is guaranteed to be a multiple of 8, then the first arg of .to_bytes
can be simplified:
return int(s, 2).to_bytes(len(s) // 8, byteorder='big')
This will raise OverflowError
if len(s)
is not a multiple of 8, which may be desirable in some circumstances.
Another option is to use double negation to perform ceiling division. For integers a & b, floor division using //
n = a // b
gives the integer n such that
n <= a/b < n + 1
Eg,
47 // 10
gives 4, and
-47 // 10
gives -5. So
-(-47 // 10)
gives 5, effectively performing ceiling division.
Thus in bitstring_to_bytes
we could do:
return int(s, 2).to_bytes(-(-len(s) // 8), byteorder='big')
However, not many people are familiar with this efficient & compact idiom, so it's generally considered to be less readable than
return (s, 2).to_bytes((len(s) + 7) // 8, byteorder='big')
这篇关于在 Python 3 中将二进制字符串转换为 bytearray的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!