Bitarray

3.8.0 · active · verified Sun Mar 29

The bitarray library (current version 3.8.0) provides an efficient object type for representing arrays of booleans, implemented as a C extension for high performance. Bitarrays behave much like standard Python lists, supporting sequence operations like slicing and concatenation, as well as bitwise operations. It allows users to choose between little-endian and big-endian representations, with eight bits packed into one byte in a contiguous memory block. The library maintains an active release cadence, with frequent updates addressing features and bug fixes.

Warnings

breaking Python 2.7 support was removed in `bitarray` 3.0.0 (October 2024). Python 3.5 support was dropped in `bitarray` 3.4.0 (May 2025). Ensure your project uses Python 3.6 or newer.
Fix: Upgrade your Python environment to 3.6+ and update your codebase to be Python 3 compatible if migrating from Python 2.7.
breaking In `bitarray` 3.0.0, the `.decode()` and `.search()` methods now return iterators, replacing the previously dedicated `.iterdecode()` and `.itersearch()` methods, which were removed. Additionally, `util.rindex()` was removed, favoring `.index(..., right=1)`, and `util.make_endian()` was removed, replaced by `bitarray(..., endian=...)`.
Fix: Refactor code to use the iterator-returning `.decode()` and `.search()`. Replace `util.rindex()` with `.index(..., right=1)` and `util.make_endian()` with the `endian` keyword argument in the `bitarray` constructor.
breaking As of `bitarray` 3.4.0, the `.endian()` *method* was removed and replaced by a `.endian` *data descriptor* (property). Attempting to call `.endian()` will result in an error.
Fix: Change calls like `my_bitarray.endian()` to accessing the attribute `my_bitarray.endian`.
gotcha Shift operations (`<<`, `>>`) on `bitarray` objects have specific, defined behavior, which may differ from expectations based on C or general Python integer shifts. The length of the bitarray is never changed; blanks are filled with 0s. Negative shifts raise `ValueError`. Shifts larger than or equal to the bitarray's length result in an all-zero bitarray.
Fix: Consult the official documentation for precise behavior of shift operations to avoid unexpected results. Ensure shift values are non-negative and within expected bounds relative to the bitarray length if a non-zero result is desired.

Install

pip install bitarray Install stable release

Imports

bitarray
```
from bitarray import bitarray
```
The primary class for creating and manipulating bitarrays.
util
```
from bitarray import util
```
A submodule containing various utility functions for bitarray objects.

Quickstart

Demonstrates creating bitarray objects, setting individual bits, extending with more bits, and initializing from strings or iterables. It also shows basic bitwise operations.

from bitarray import bitarray

# Create an empty bitarray of length 10, initialized to zeros
a = bitarray(10)
print(f"Initial bitarray: {a} (length: {len(a)})")

# Set individual bits
a[0] = 1
a[3] = 1
print(f"After setting bits: {a}")

# Append bits
a.append(0)
a.extend('101') # Extend with a string of '0's and '1's
print(f"After appending and extending: {a} (length: {len(a)})")

# Initialize from a string or list
b = bitarray('1101_0010') # Underscores are ignored
c = bitarray([True, False, True, True])
print(f"Bitarray from string: {b}")
print(f"Bitarray from list: {c}")

# Perform bitwise operations
d = b & c # Bitwise AND
e = b | c # Bitwise OR
print(f"Bitwise AND (b & c): {d}")
print(f"Bitwise OR (b | c): {e}")

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