How to create an array of bits in Python?

Question

How can I declare a bit array of a very large size, say 6 million bits?

See also http://stackoverflow.com/questions/2147848/how-do-i-represent-and-work-with-n-bit-vectors-in-python -- hesitant to mark as duplicate. — tripleee, May 26 '16 at 05:16

score 45 · Accepted Answer · answered Jul 26 '12 at 12:25

45

from bitarray import bitarray

a = bitarray(2**20)

You can check out more info about this module at http://pypi.python.org/pypi/bitarray/

answered Jul 26 '12 at 12:25

SJP

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_bitarray_ does not seem to be in the standard python, but is instead a feature offered by _pypy_. – zvezda Apr 27 '15 at 05:45
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I think you mean *pip* – Uxío Apr 28 '15 at 18:45
15

I think you mean “included in *PyPI*”, the Python Package Index. :p – Gandaro May 24 '15 at 12:41

Scott Griffiths · Answer 2 · 2020-05-15T11:33:36.293

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The bitstring module may help:

from bitstring import BitArray
a = BitArray(6000000)

This will take less than a megabyte of memory, and it's easy to set, read, slice and interpret bits. Unlike the bitarray module it's pure Python, plus it works for Python 3.

See the documentation for more details.

edited May 15 '20 at 11:33

answered Aug 11 '12 at 21:28

Scott Griffiths

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score 11 · Answer 3 · edited Nov 14 '17 at 02:15

This one-liner converts bytes to a list of True/False bit values. Might be not performant for 6M bits but for small flags it should be fine and does not need additional dependencies.

>>> flags = bytes.fromhex(b"beef")
>>> bits =  [flags[i//8] & 1 << i%8 != 0 for i in range(len(flags) * 8)]
>>> print(bits)
[False, True, True, True, True, True, False, True, True, True, True, True, False, True, True, True]

score 11 · Answer 4 · answered Nov 21 '18 at 19:51

Quite easily

bitarray60000 = 1<<60000

With that, you can use bitshift operator to your heart content. For instance, position 2 set True would be:

bitarray60000 | 1<<2

Getting bit from position 2

bitarray60000 & 1<<2

I guess the idea is quite simple. Though some operations might be tricky.

score 9 · Answer 5 · answered May 15 '15 at 04:33

9

Get the bitarray module using

pip install bitarray

Then, this code will create a bit array of size 6 million,

from bitarray import bitarray
bit_array = bitarray(6000000)

You can initialize all the bits to zero using

bit_array.setall(0)

To set a particular bit, say bit number 25, to 1, do this:

bit_array[25]=1

answered May 15 '15 at 04:33

Tarun

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I updated `pip` beforehand see [link](https://packaging.python.org/installing/) Then execute `python -m pip install bitarray` on Windows. – yW0K5o Feb 23 '17 at 19:09

How to create an array of bits in Python?

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