bitarray

2.3.8 verified Tue May 12 auth: no python install: verified

Efficient boolean arrays implemented as a C extension for Python. Provides bit-level operations, packed representations, and performance comparable to NumPy for bit manipulation. Current version 2.3.8. Released under PSF license.

pip install bitarray

Common errors

error TypeError: 'bitarray' object is not callable ↓

cause Trying to call a bitarray object as a function, e.g., a() instead of a[index].

fix

Use indexing to access bits: bit = a[0]

error ValueError: bitarray must not contain whitespace ↓

cause Constructing bitarray from a string that contains spaces or other invalid characters.

fix

Remove whitespace: bitarray('11001010') not bitarray('1100 1010')

error ImportError: cannot import name 'bitarray' from 'bitarray' ↓

cause Incorrect import attempt or missing installation/conflict with another package named bitarray.

fix

Use 'from bitarray import bitarray'. If you already installed, check for version conflicts: 'pip install --upgrade bitarray'

Warnings

breaking bitarray objects are not hashable. Attempting to use them as dictionary keys or in sets will raise TypeError. ↓

fix Convert to bytes or tuple for hashing, e.g., key = a.tobytes()

deprecated The 'bitarray.endian()' method is deprecated in favor of the 'endian' property in version 2.0+. ↓

fix Use 'bitarray.endian' (property) instead of 'bitarray.endian()' (method).

gotcha When creating a bitarray from an integer, the integer is treated as the length (number of bits), not as the initial bits. bitarray(8) creates 8 zero bits, not a bitarray with one bit set at position 3. ↓

fix Use bitarray('111') for specific bits or bitarray(8) for an all-zero array of given length.

gotcha The 'count()' method with 'value' parameter default is 1. bitarray('110').count() returns 2 (counts 1s). Use count(0) to count zeros. ↓

fix Explicitly pass value=0 for zero count: mybitarray.count(0).

Install compatibility verified last tested: 2026-05-12

python os / libc status wheel install import disk

3.10 alpine (musl) wheel - 0.00s 19.0M

3.10 alpine (musl) - - 0.00s 19.0M

3.10 slim (glibc) wheel 2.1s 0.00s 20M

3.10 slim (glibc) - - 0.00s 20M

3.11 alpine (musl) wheel - 0.00s 21.2M

3.11 alpine (musl) - - 0.01s 21.2M

3.11 slim (glibc) wheel 1.9s 0.00s 22M

3.11 slim (glibc) - - 0.00s 22M

3.12 alpine (musl) wheel - 0.00s 13.0M

3.12 alpine (musl) - - 0.00s 13.0M

3.12 slim (glibc) wheel 1.7s 0.00s 14M

3.12 slim (glibc) - - 0.00s 14M

3.13 alpine (musl) wheel - 0.00s 12.8M

3.13 alpine (musl) - - 0.00s 12.6M

3.13 slim (glibc) wheel 1.7s 0.00s 13M

3.13 slim (glibc) - - 0.00s 13M

3.9 alpine (musl) wheel - 0.00s 18.5M

3.9 alpine (musl) - - 0.00s 18.5M

3.9 slim (glibc) wheel 2.4s 0.00s 19M

3.9 slim (glibc) - - 0.00s 19M

Imports

Bitarray

wrong

from bitarray import Bitarray

correct

from bitarray import bitarray

Class name is lowercase 'bitarray'.

bitarray
wrong
```
import bitarray
```
correct
```
from bitarray import bitarray
```
While 'import bitarray' works, you need to use 'bitarray.bitarray()'. Direct import of the class is common.

Quickstart last tested: 2026-04-24

Create bitarrays, perform bitwise operations, and convert to bytes.

from bitarray import bitarray
# Create a bitarray of 8 zero bits
a = bitarray(8)
print('Length:', len(a))  # 8
# Set bits from a binary string
a = bitarray('11001010')
print(a)  # bitarray('11001010')
# Bitwise operations
b = bitarray('11110000')
c = a & b
print(c)  # bitarray('11000000')
# Convert to bytes
packed = a.tobytes()
print('Bytes:', packed)