如何将位数组转换为 python 中的 integer

Question

Suppose I define some bitarray in python using the following code:

from bitarray import bitarray
d=bitarray('0'*30)
d[5]=1

How can I convert d to its integer representation? In addition, how can I perform manipulations such as d&(d+1) with bitarrays?

Answer 1

To convert a bitarray to its integer form you can use the struct module:

Code:

from bitarray import bitarray
import struct

d = bitarray('0' * 30, endian='little')

d[5] = 1
print(struct.unpack("<L", d)[0])

d[6] = 1
print(struct.unpack("<L", d)[0])

Outputs:

32
96

Answer 2

from bitarray import bitarray
d=bitarray('0'*30)
d[5]=1

i = 0
for bit in d:
    i = (i << 1) | bit

print i

output: 16777216.

Answer 3

A simpler approach that I generally use is

d=bitarray('0'*30)
d[5]=1
print(int(d.to01(),2))

Code wise this may not be that efficient, as it converts the bit array to a string and then back to an int, but it is much more concise to read so probably better in shorter scripts.

Answer 4

Bitarray 1.2.0 added a utility module, bitarray.util , which includes a functions converting bitarrays to integers and vice versa. The functions are called int2ba and ba2int . Please see here for the exact details: https://github.com/ilanschnell/bitarray

Answer 5

As Ilan Schnell pointed out there is a ba2int() method found in the bitarray.util module.

>>> from bitarray import bitarray
>>> from bitarray.util import ba2int
>>> d = bitarray('0' * 30)
>>> d[5] = 1
>>> d
bitarray('000001000000000000000000000000')
>>> ba2int(d)
16777216

From that same module there is a zeros() method that changes the first three lines to

>>> from bitarray import bitarray
>>> from bitarray.util import ba2int, zeros
>>> d = zeros(30)

Answer 6

You can use int :

>>> int(d.to01(), base=2)
>>> 16777216

The bitarray.to01 method produces a bit string from the bit array, and int(<bit string>, base=2) converts it to a decimal integer.