Bytearray

A bytearray is a mutable sequence of integers in the range 0 to 255, used to store and manipulate binary data. It is similar to the immutable bytes type, but supports in-place modification and dynamic resizing. Like other sequences, it supports iteration, indexing, and slicing.

A bytearray can be created in several ways. Calling bytearray() produces an empty buffer. Passing an integer n creates a buffer of length n filled with zeros. Providing an iterable of integers initializes the buffer with those values. You can also construct it from an existing bytes-like object or from a string by encoding it (bytearray(str, encoding)). A memoryview can also be used to initialize or view a bytearray.

Bytearrays are mutable and support common sequence operations. Elements can be assigned individual values, for example b[0] = 65. They provide methods to modify the contents efficiently, including append(x) to add a single value, extend(iterable) to add multiple values, insert(i, x), remove(x), pop([i]), clear(), and reverse(). Slicing a bytearray returns a new bytearray, preserving mutability of the slice.

Conversions and interoperability are straightforward. A bytearray can be converted to immutable bytes with bytes(b) or to a memoryview for zero-copy access. It is suitable for binary I/O with files opened in binary mode, network sockets, and interfaces requiring mutable buffers. It is also commonly used with the struct module for packing and unpacking binary data.

Notes: all stored values must be integers in the range 0–255; attempting to assign or append values outside this range raises a ValueError. Bytearrays offer a practical balance between memory efficiency and mutability for binary data processing.

See also: bytes, memoryview.