BitArray

class BitArray(auto: BitsType | int | None, /, length: int | None = None, offset: int | None = None, **kwargs)

The Bits class is the base class for BitArray and so (with the exception of __hash__) all of its methods are also available for BitArray objects. The initialiser is the same as for Bits.

A BitArray is a mutable Bits, and so the one thing all of the methods listed here have in common is that they can modify the contents of the bitstring.

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Methods

BitArray.append(bs: BitsType) → None

Join a BitArray to the end of the current BitArray.

>>> s = BitArray('0xbad')
>>> s.append('0xf00d')
>>> s
BitArray('0xbadf00d')

BitArray.byteswap(fmt: str | int | Iterable[int] | None = None, start: int | None = None, end: int | None = None, repeat: bool = True) → int

Change the endianness of the BitArray in-place according to fmt. Return the number of swaps done.

The fmt can be an integer, an iterable of integers or a compact format string similar to those used in pack (described in Compact format strings). It defaults to 0, which means reverse as many bytes as possible. The fmt gives a pattern of byte sizes to use to swap the endianness of the BitArray. Note that if you use a compact format string then the endianness identifier (<, > or =) is not needed, and if present it will be ignored.

start and end optionally give a slice to apply the transformation to (it defaults to the whole BitArray). If repeat is True then the byte swapping pattern given by the fmt is repeated in its entirety as many times as possible.

>>> s = BitArray('0x00112233445566')
>>> s.byteswap(2)
3
>>> s
BitArray('0x11003322554466')
>>> s.byteswap('h')
3
>>> s
BitArray('0x00112233445566')
>>> s.byteswap([2, 5])
1
>>> s
BitArray('0x11006655443322')

It can also be used to swap the endianness of the whole BitArray.

>>> s = BitArray('uintle32=1234')
>>> s.byteswap()
>>> print(s.uintbe)
1234

BitArray.clear() → None

Removes all bits from the bitstring.

s.clear() is equivalent to del s[:] and simply makes the bitstring empty.

BitArray.insert(bs: BitsType, pos: int) → None

Inserts bs at pos.

When used with the BitStream class the pos is optional, and if not present the current bit position will be used. After insertion the property pos will be immediately after the inserted bitstring.

>>> s = BitStream('0xccee')
>>> s.insert('0xd', 8)
>>> s
BitStream('0xccdee')
>>> s.insert('0x00')
>>> s
BitStream('0xccd00ee')

BitArray.invert(pos: int | Iterable[int] | None = None) → None

Inverts one or many bits from 1 to 0 or vice versa.

pos can be either a single bit position or an iterable of bit positions. Negative numbers are treated in the same way as slice indices and it will raise IndexError if pos < -len(s) or pos > len(s). The default is to invert the entire BitArray.

>>> s = BitArray('0b111001')
>>> s.invert(0)
>>> s.bin
'011001'
>>> s.invert([-2, -1])
>>> s.bin
'011010'
>>> s.invert()
>>> s.bin
'100101'

BitArray.overwrite(bs: BitsType, pos: int) → None

Replaces the contents of the current BitArray with bs at pos.

When used with the BitStream class the pos is optional, and if not present the current bit position will be used. After insertion the property pos will be immediately after the overwritten bitstring.

>>> s = BitArray(length=10)
>>> s.overwrite('0b111', 3)
>>> s
BitArray('0b0001110000')
>>> s.pos
6

BitArray.prepend(bs: BitsType) → None

Inserts bs at the beginning of the current BitArray.

>>> s = BitArray('0b0')
>>> s.prepend('0xf')
>>> s
BitArray('0b11110')

BitArray.replace(old: BitsType, new: BitsType, start: int | None = None, end: int | None = None, count: int | None = None, bytealigned: bool | None = None) → int

Finds occurrences of old and replaces them with new. Returns the number of replacements made.

If bytealigned is True then replacements will only be made on byte boundaries. start and end give the search range and default to the start and end of the bitstring. If count is specified then no more than this many replacements will be made.

>>> s = BitArray('0b0011001')
>>> s.replace('0b1', '0xf')
3
>>> print(s.bin)
0011111111001111
>>> s.replace('0b1', '', count=6)
6
>>> print(s.bin)
0011001111

BitArray.reverse(start: int | None = None, end: int | None = None) → None

Reverses bits in the BitArray in-place.

start and end give the range of bits to reverse and default to the start and end of the bitstring.

>>> a = BitArray('0b000001101')
>>> a.reverse()
>>> a.bin
'101100000'
>>> a.reverse(0, 4)
>>> a.bin
'110100000'

BitArray.rol(bits: int, start: int | None = None, end: int | None = None) → None

Rotates the contents of the BitArray in-place by bits bits to the left.

start and end define the slice to use and default to the start and end of the bitstring.

Raises ValueError if bits < 0.

>>> s = BitArray('0b01000001')
>>> s.rol(2)
>>> s.bin
'00000101'

BitArray.ror(bits: int, start: int | None = None, end: int | None = None) → None

Rotates the contents of the BitArray in-place by bits bits to the right.

start and end define the slice to use and default to the start and end of the bitstring.

Raises ValueError if bits < 0.

BitArray.set(value: bool, pos: int | Iterable[int] | None = None) → None

Sets one or many bits to either 1 (if value is True) or 0 (if value isn’t True). pos can be either a single bit position or an iterable of bit positions. Negative numbers are treated in the same way as slice indices and it will raise IndexError if pos < -len(s) or pos > len(s). The default is to set every bit in the BitArray.

Using s.set(True, x) can be more efficient than other equivalent methods such as s[x] = 1, s[x] = "0b1" or s.overwrite('0b1', x), especially if many bits are being set. In particular using a range object as an iterable is treated as a special case and is done efficiently.

>>> s = BitArray('0x0000')
>>> s.set(True, -1)
>>> print(s)
0x0001
>>> s.set(1, (0, 4, 5, 7, 9))
>>> s.bin
'1000110101000001'
>>> s.set(0)
>>> s.bin
'0000000000000000'
>>> s.set(1, range(0, len(s), 2))
>>> s.bin
'1010101010101010'

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Properties

Note that the bin, oct, hex, int, uint and float properties can all be shortened to their initial letter. Properties can also have a length in bits appended to them to make properties such as u8 or floatle64 (with the exception of the bytes property which uses a unit of bytes instead of bits, so bytes4 is 32 bits long). These properties with lengths can be used to quickly create a new bitstring.

>>> a = BitArray()
>>> a.f32 = 17.6
>>> a.h
'418ccccd'
>>> a.i7 = -1
>>> a.b
'1111111'

The binary interpretation properties of the Bits class all become writable in the BitArray class.

For integer types, the properties can have a bit length appended to it such as u32 or int5 to specify the new length of the bitstring. Using a length too small to contain the value given will raise a CreationError.

When used as a setter without a new length the value must fit into the current length of the BitArray, else a ValueError will be raised.

>>> s = BitArray('0xf3')
>>> s.int
-13
>>> s.int = 1232
ValueError: int 1232 is too large for a BitArray of length 8.

Other types also have restrictions on their lengths, and using an invalid length will raise a CreationError. For example trying to create a 20 bit floating point number or a two bit bool will raise this exception.

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Special Methods

BitArray.__delitem__(key)

del s[start:end:step]

Deletes the slice specified.

BitArray.__iadd__(bs)

s1 += s2

Appends bs to the current bitstring.

Note that for BitArray objects this will be an in-place change, whereas for Bits objects using += will not call this method - instead a new object will be created (it is equivalent to a copy and an __add__).

>>> s = BitArray(ue=423)
>>> s += BitArray(ue=12)
>>> s.read('ue')
423
>>> s.read('ue')
12

BitArray.__iand__(bs)

s &= bs

In-place bit-wise AND between two bitstrings. If the two bitstrings are not the same length then a ValueError is raised.

BitArray.__ilshift__(n)

s <<= n

Shifts the bits in-place n bits to the left. The n right-most bits will become zeros and bits shifted off the left will be lost.

BitArray.__imul__(n)

s *= n

In-place concatenation of n copies of the current bitstring.

>>> s = BitArray('0xbad')
>>> s *= 3
>>> s.hex
'badbadbad'

BitArray.__ior__(bs)

s |= bs

In-place bit-wise OR between two bitstrings. If the two bitstrings are not the same length then a ValueError is raised.

BitArray.__irshift__(n)

s >>= n

Shifts the bits in-place n bits to the right. The n left-most bits will become zeros and bits shifted off the right will be lost.

BitArray.__ixor__(bs)

s ^= bs

In-place bit-wise XOR between two bitstrings. If the two bitstrings are not the same length then a ValueError is raised.

BitArray.__setitem__(key, value)

s1[start:end:step] = s2

Replaces the slice specified with a new value.

>>> s = BitArray('0x00000000')
>>> s[::8] = '0xf'
>>> print(s)
0x80808080
>>> s[-12:] = '0xf'
>>> print(s)
0x80808f