在Python中将二进制表示形式转换为带符号的64位整数

Question

Against the advice of online resources, I'm using Python to do some simple bit shifting in one of my scripts. The bit shifting is fine, it's representing the result that's difficult. Let me explain.

I have a 64 bit binary representation

1000010101010111010101010101010101010101010101010111010101010101

which, when represented as a signed integer, should be negative. However, Python defaults to type long , preventing the number from being signed by the first bit, yielding the number 9608242155010487637 .

How can I get Python to recognize the sign bit in 64 bits?

To clarify, I'm using Python 2.7.

Answer 1

You can use struct , like this:

>>> import struct
>>> struct.unpack('l',struct.pack('P',
int('1000010101010111010101010101010101010101010101010111010101010101',
2)))
#=> (-8838501918699063979,)

The result is a tuple, which you can then request the first element of:

>>> struct.unpack('l',struct.pack('P',
int('1000010101010111010101010101010101010101010101010111010101010101',
2)))[0]
#=> -8838501918699063979

Answer 2

Try the bitstring module:

>>> from bitstring import BitArray
>>> s = '1000010101010111010101010101010101010101010101010111010101010101'
>>> BitArray(bin=s).int
-8838501918699063979