Bits

The Bits class is the simplest type in the bitstring module, and represents an immutable sequence of bits. This is the best class to use if you will not need to modify the data after creation and don’t need streaming methods.

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

Creates a new bitstring. You must specify either no initialiser, just an ‘auto’ value as the first parameter, or a keyword argument such as bytes, bin, hex, oct, uint, int, float, bool or filename (for example) to indicate the data type. If no initialiser is given then a zeroed bitstring of length bits is created.

The initialiser for the Bits class is precisely the same as for BitArray, BitStream and ConstBitStream.

offset is available when using the bytes or filename initialisers. It gives a number of bits to ignore at the start of the bitstring.

Specifying length is mandatory when using the various integer initialisers. It must be large enough that a bitstring can contain the integer in length bits. It must also be specified for the float initialisers (the only valid values are 16, 32 and 64). It is optional for the bytes and filename initialisers and can be used to truncate data from the end of the input value.

>>> s1 = Bits(hex='0x934')
>>> s2 = Bits(oct='0o4464')
>>> s3 = Bits(bin='0b001000110100')
>>> s4 = Bits(int=-1740, length=12)
>>> s5 = Bits(uint=2356, length=12)
>>> s6 = Bits(bytes=b'\x93@', length=12)
>>> s1 == s2 == s3 == s4 == s5 == s6
True

See also The auto initialiser, which allows many different types to be used to initialise a bitstring.

>>> s = Bits('uint12=32, 0b110')
>>> t = Bits('0o755, ue=12, int:3=-1')

In the methods below we use BitsType to indicate that any of the types that can auto initialise can be used.

Methods

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

Returns True if all of the specified bits are all set to value, otherwise returns False.

If value is True then 1 bits are checked for, otherwise 0 bits are checked for.

pos should be an iterable of bit positions. Negative numbers are treated in the same way as slice indices and it will raise an IndexError if pos < -len(s) or pos > len(s). It defaults to the whole bitstring.

>>> s = Bits('int15=-1')
>>> s.all(True, [3, 4, 12, 13])
True
>>> s.all(1)
True
Bits.any(value: bool, pos: Iterable[int] | None = None) → bool

Returns True if any of the specified bits are set to value, otherwise returns False.

If value is True then 1 bits are checked for, otherwise 0 bits are checked for.

pos should be an iterable of bit positions. Negative numbers are treated in the same way as slice indices and it will raise an IndexError if pos < -len(s) or pos > len(s). It defaults to the whole bitstring.

>>> s = Bits('0b11011100')
>>> s.any(False, range(6))
True
>>> s.any(1)
True
Bits.copy() → Bits

Returns a copy of the bitstring.

s.copy() is equivalent to the shallow copy s[:] and creates a new copy of the bitstring in memory.

Bits.count(value: bool) → int

Returns the number of bits set to value.

value can be True or False or anything that can be cast to a bool, so you could equally use 1 or 0.

>>> s = BitArray(1000000)
>>> s.set(1, [4, 44, 444444])
>>> s.count(1)
3
>>> s.count(False)
999997

If you need to count more than just single bits you can use findall, for example len(list(s.findall('0xabc'))). Note that if the bitstring is very sparse, as in the example here, it could be quicker to find and count all the set bits with something like len(list(s.findall('0b1'))). For bitstrings with more entropy the count method will be much quicker than finding.

Bits.cut(bits: int, start: int | None = None, end: int | None = None, count: int | None = None) → Iterator[Bits]

Returns a generator for slices of the bitstring of length bits.

At most count items are returned and the range is given by the slice [start:end], which defaults to the whole bitstring.

>>> s = BitArray('0x1234')
>>> for nibble in s.cut(4):
...     s.prepend(nibble)
>>> print(s)
0x43211234
Bits.endswith(bs: BitsType, start: int | None = None, end: int | None = None) → bool

Returns True if the bitstring ends with the sub-string bs, otherwise returns False.

A slice can be given using the start and end bit positions and defaults to the whole bitstring.

>>> s = Bits('0x35e22')
>>> s.endswith('0b10, 0x22')
True
>>> s.endswith('0x22', start=13)
False
Bits.find(bs: BitsType, start: int | None = None, end: int | None = None, bytealigned: bool | None = None) → Tuple[int] | Tuple[()]

Searches for bs in the current bitstring and sets pos to the start of bs and returns it in a tuple if found, otherwise it returns an empty tuple.

The reason for returning the bit position in a tuple is so that it evaluates as True even if the bit position is zero. This allows constructs such as if s.find('0xb3'): to work as expected.

If bytealigned is True then it will look for bs only at byte aligned positions (which is generally much faster than searching for it in every possible bit position). start and end give the search range and default to the whole bitstring.

>>> s = Bits('0x0023122')
>>> s.find('0b000100', bytealigned=True)
(16,)
Bits.findall(bs: BitsType, start: int | None = None, end: int | None = None, count: int | None = None, bytealigned: bool | None = None) → Iterable[int]

Searches for all occurrences of bs (even overlapping ones) and returns a generator of their bit positions.

If bytealigned is True then bs will only be looked for at byte aligned positions. start and end optionally define a search range and default to the whole bitstring.

The count parameter limits the number of items that will be found - the default is to find all occurrences.

>>> s = Bits('0xab220101')*5
>>> list(s.findall('0x22', bytealigned=True))
[8, 40, 72, 104, 136]
classmethod Bits.fromstring(s: str, /) → Bits

Creates a new bitstring from the formatted string s. It is equivalent to creating a new bitstring using s as the first parameters, but can be clearer to write and will be slightly faster.

>>> b1 = Bits('int16=91')
>>> b2 = Bits.fromstring('int16=91')
>>> b1 == b2
True
Bits.join(sequence: Iterable) → Bits

Returns the concatenation of the bitstrings in the iterable sequence joined with self as a separator.

>>> s = Bits().join(['0x0001ee', 'uint:24=13', '0b0111'])
>>> print(s)
0x0001ee00000d7

>>> s = Bits('0b1').join(['0b0']*5)
>>> print(s.bin)
010101010
Bits.pp(fmt: str | None = None, width: int = 120, sep: str = ' ', show_offset: bool = True, stream: TextIO = sys.stdout) → None

Pretty print the bitstring’s value according to the fmt. Either a single, or two comma separated formats can be specified, together with options for setting the maximum display width, the number of bits to display in each group, and the separator to print between groups.

>>> s = Bits('0b10111100101101001')*20
>>> s.pp(width=80)
<Bits, fmt='bin8, hex', length=340 bits> [
  0: 10111100 10110100 11011110 01011010 01101111 00101101 : bc b4 de 5a 6f 2d
 48: 00110111 10010110 10011011 11001011 01001101 11100101 : 37 96 9b cb 4d e5
 96: 10100110 11110010 11010011 01111001 01101001 10111100 : a6 f2 d3 79 69 bc
144: 10110100 11011110 01011010 01101111 00101101 00110111 : b4 de 5a 6f 2d 37
192: 10010110 10011011 11001011 01001101 11100101 10100110 : 96 9b cb 4d e5 a6
240: 11110010 11010011 01111001 01101001 10111100 10110100 : f2 d3 79 69 bc b4
288: 11011110 01011010 01101111 00101101 00110111 10010110 : de 5a 6f 2d 37 96
] + trailing_bits = 0x9

>>> s.pp('int20, hex', width=80, show_offset=False, sep=' / ')
<Bits, fmt='int20, hex', length=340 bits> [
-275635 / -107921 /  185209 /  433099 : bcb4d / e5a6f / 2d379 / 69bcb
 319066 /  455379 /  497307 / -215842 : 4de5a / 6f2d3 / 7969b / cb4de
 370418 / -182378 / -410444 / -137818 : 5a6f2 / d3796 / 9bcb4 / de5a6
 -53961 / -431684 / -307739 / -364755 : f2d37 / 969bc / b4de5 / a6f2d
 227689                               : 37969
]

The available formats are any fixed-length dtypes, for example 'bin', 'oct', 'hex' and 'bytes' together with types with explicit lengths such as 'uint5' and 'float16'. A bit length can be specified after the format (with an optional :) to give the number of bits represented by each group, otherwise the default is based on the format or formats selected.

For the 'bytes' format, characters from the ‘Latin Extended-A’ unicode block are used for non-ASCII and unprintable characters.

If the bitstring cannot be represented in a format due to its length not being a multiple of the number of bits represented by each character then an InterpretError will be raised.

An output stream can be specified. This should be an object with a write method and the default is sys.stdout.

By default the output will have colours added in the terminal. This can be disabled - see bitstring.options.no_color for more information.

Bits.rfind(bs: BitsType, start: int | None = None, end: int | None = None, bytealigned: bool | None = None) → Tuple[int] | Tuple[()]

Searches backwards for bs in the current bitstring and sets pos to the start of bs and returns it in a tuple if found, otherwise it returns an empty tuple.

The reason for returning the bit position in a tuple is so that it evaluates as True even if the bit position is zero. This allows constructs such as if s.rfind('0xb3'): to work as expected.

If bytealigned is True then it will look for bs only at byte aligned positions. start and end give the search range and default to 0 and len respectively.

Note that as it’s a reverse search it will start at end and finish at start.

>>> s = Bits('0o031544')
>>> s.rfind('0b100')
(15,)
>>> s.rfind('0b100', end=17)
(12,)
Bits.split(delimiter: BitsType, start: int | None = None, end: int | None = None, count: int | None = None, bytealigned: bool | None = None) → Iterable[Bits]

Splits the bitstring into sections that start with delimiter. Returns a generator for bitstring objects.

The first item generated is always the bits before the first occurrence of delimiter (even if empty). A slice can be optionally specified with start and end, while count specifies the maximum number of items generated.

If bytealigned is True then the delimiter will only be found if it starts at a byte aligned position.

>>> s = Bits('0x42423')
>>> [bs.bin for bs in s.split('0x4')]
['', '01000', '01001000', '0100011']
Bits.startswith(bs: BitsType, start: int | None = None, end: int | None = None) → bool

Returns True if the bitstring starts with the sub-string bs, otherwise returns False.

A slice can be given using the start and end bit positions and defaults to the whole bitstring.

>>> s = BitArray('0xef133')
>>> s.startswith('0b111011')
True
Bits.tobitarray() → bitarray.bitarray

Returns the bitstring as a bitarray object.

Converts the bitstring to an equivalent bitarray object from the bitarray package. This shouldn’t be confused with the BitArray type provided in the bitstring package - the bitarray package is a separate third-party way of representing binary objects.

Note that BitStream and ConstBitStream types that have a bit position do support this method but the bit position information will be lost.

Bits.tobytes() → bytes

Returns the bitstring as a bytes object.

The returned value will be padded at the end with between zero and seven 0 bits to make it byte aligned. This differs from using the plain bytes property which will not pad with zero bits and instead raises an exception if the bitstring is not a whole number of bytes long.

This method can also be used to output your bitstring to a file - just open a file in binary write mode and write the function’s output.

>>> s = Bits(bytes=b'hello')
>>> s += '0b01'
>>> s.tobytes()
b'hello@'

This is equivalent to casting to a bytes object directly:

>>> bytes(s)
b'hello@'
Bits.tofile(f: BinaryIO) → None

Writes the bitstring to the file object f, which should have been opened in binary write mode.

The data written will be padded at the end with between zero and seven 0 bits to make it byte aligned.

>>> f = open('newfile', 'wb')
>>> Bits('0x1234').tofile(f)
Bits.unpack(fmt: str | list[str | int], **kwargs) → list[float | int | str | None | Bits]

Interprets the whole bitstring according to the fmt string or iterable and returns a list of bitstring objects.

A dictionary or keyword arguments can also be provided. These will replace length identifiers in the format string.

fmt is an iterable or a string with comma separated tokens that describe how to interpret the next bits in the bitstring. See the Format tokens for details.

>>> s = Bits('int4=-1, 0b1110')
>>> i, b = s.unpack('int:4, bin')

If a token doesn’t supply a length (as with bin above) then it will try to consume the rest of the bitstring. Only one such token is allowed.

The unpack method is a natural complement of the pack function.

s = bitstring.pack('uint10, hex, int13, 0b11', 130, '3d', -23)
a, b, c, d = s.unpack('uint10, hex, int13, bin2')

Properties

The many ways to interpret bitstrings can be accessed via properties. These properties will be read-only for a Bits object, but are also writable for derived mutable types such as BitArray and BitStream.

Properties can also have a length in bits appended to them to such as u8 or f64 (for the bytes property the length is interpreted in bytes instead of bits). These properties with lengths will cause an InterpretError to be raised if the bitstring is not of the specified length.

This list isn’t exhaustive - see for example Exotic Floating Point Formats for information on bfloats and many 8-bit and smaller floating point formats. Also see Exponential-Golomb Codes for some interesting variable length integer formats.

Note that the bin, oct, hex, int, uint and float properties can all be shortened to their initial letter.

Bits.bin: str

Property for the representation of the bitstring as a binary string. Can be shortened to just b.

Bits.bool: bool

Property for representing the bitstring as a boolean (True or False).

If the bitstring is not a single bit then the getter will raise an InterpretError.

Bits.bytes: bytes

Property representing the underlying byte data that contains the bitstring.

When used as a getter the bitstring must be a whole number of byte long or a InterpretError will be raised.

An alternative is to use the tobytes method, which will pad with between zero and seven 0 bits to make it byte aligned if needed.

>>> s = Bits('0x12345678')
>>> s.bytes
b'\x124Vx'
Bits.hex: str

Property representing the hexadecimal value of the bitstring. Can be shortened to just h.

If the bitstring is not a multiple of four bits long then getting its hex value will raise an InterpretError.

>>> s = Bits(bin='1111 0000')
>>> s.hex
'f0'
Bits.int: int

Property for the signed two’s complement integer representation of the bitstring. Can be shortened to just i.

Bits.intbe: int

Property for the byte-wise big-endian signed two’s complement integer representation of the bitstring.

Only valid for whole-byte bitstrings, in which case it is equal to s.int, otherwise an InterpretError is raised.

Bits.intle: int

Property for the byte-wise little-endian signed two’s complement integer representation of the bitstring.

Only valid for whole-byte bitstring, in which case it is equal to s[::-8].int, i.e. the integer representation of the byte-reversed bitstring.

Bits.intne: int

Property for the byte-wise native-endian signed two’s complement integer representation of the bitstring.

Only valid for whole-byte bitstrings, and will equal either the big-endian or the little-endian integer representation depending on the platform being used.

Bits.float: float
Bits.floatbe: float

Property for the floating point representation of the bitstring. Can be shortened to just f.

The bitstring must be 16, 32 or 64 bits long to support the floating point interpretations, otherwise an InterpretError will be raised.

If the underlying floating point methods on your machine are not IEEE 754 compliant then using the float interpretations is undefined (this is unlikely unless you’re on some very unusual hardware).

The float property is bit-wise big-endian, which as all floats must be whole-byte is exactly equivalent to the byte-wise big-endian floatbe.

Bits.floatle: float

Property for the byte-wise little-endian floating point representation of the bitstring.

Bits.floatne: float

Property for the byte-wise native-endian floating point representation of the bitstring.

Bits.len: int
Bits.length: int

Read-only property that give the length of the bitstring in bits (len and length are equivalent).

Using the len() built-in function is preferred in almost all cases, but these properties are available for backward compatibility. The only occasion where the properties are needed is if a 32-bit build of Python is being used and you have a bitstring whose length doesn’t fit in a 32-bit unsigned integer. In that case len(s) may fail with an OverflowError, whereas s.len will still work. With 64-bit Python the problem shouldn’t occur unless you have more than a couple of exabytes of data!

Bits.oct: str

Property for the octal representation of the bitstring. Can be shortened to just o.

If the bitstring is not a multiple of three bits long then getting its octal value will raise a InterpretError.

>>> s = Bits('0b111101101')
>>> s.oct
'755'
>>> s.oct = '01234567'
>>> s.oct
'01234567'
Bits.uint: int

Property for the unsigned base-2 integer representation of the bitstring. Can be shortened to just u.

Bits.uintbe: int

Property for the byte-wise big-endian unsigned base-2 integer representation of the bitstring.

Bits.uintle: int

Property for the byte-wise little-endian unsigned base-2 integer representation of the bitstring.

Bits.uintne: int

Property for the byte-wise native-endian unsigned base-2 integer representation of the bitstring.

Special Methods

Bits.__add__(bs)
Bits.__radd__(bs)

s1 + s2

Concatenate two bitstring objects and return the result. Either bitstring can be ‘auto’ initialised.

s = Bits(ue=132) + '0xff'
s2 = '0b101' + s
Bits.__and__(bs)
Bits.__rand__(bs)

s1 & s2

Returns the bit-wise AND between two bitstrings, which must have the same length otherwise a ValueError is raised.

>>> print(Bits('0x33') & '0x0f')
0x03
Bits.__bool__()

if s:

Returns False if the bitstring is empty (has zero length), otherwise returns True.

>>> bool(Bits())
False
>>> bool(Bits('0b0000010000'))
True
>>> bool(Bits('0b0000000000'))
True
Bits.__contains__(bs)

bs in s

Returns True if bs can be found in the bitstring, otherwise returns False.

Similar to using find, except that you are only told if it is found, and not where it was found.

>>> '0b11' in Bits('0x06')
True
>>> '0b111' in Bits('0x06')
False
Bits.__copy__()

s2 = copy.copy(s1)

This allows the copy module to correctly copy bitstrings. Other equivalent methods are to initialise a new bitstring with the old one or to take a complete slice.

>>> import copy
>>> s = Bits('0o775')
>>> s_copy1 = copy.copy(s)
>>> s_copy2 = Bits(s)
>>> s_copy3 = s[:]
>>> s == s_copy1 == s_copy2 == s_copy3
True
Bits.__eq__(bs)

s1 == s2

Compares two bitstring objects for equality, returning True if they have the same binary representation, otherwise returning False.

>>> Bits('0o7777') == '0xfff'
True
>>> a = Bits(uint=13, length=8)
>>> b = Bits(uint=13, length=10)
>>> a == b
False

If you have a different criterion you wish to use then code it explicitly, for example a.int == b.int could be true even if a == b wasn’t (as they could be different lengths).

Bits.__getitem__(key)

s[start:end:step]

Returns a slice of the bitstring.

The usual slice behaviour applies.

>>> s = Bits('0x0123456')
>>> s[4:8]
Bits('0x1')
>>> s[1::8] # 1st, 9th, 17th and 25th bits
Bits('0x3')

If a single element is asked for then either True or False will be returned.

>>> s[0]
False
>>> s[-1]
True
Bits.__hash__()

hash(s)

Returns an integer hash of the Bits.

This method is not available for the BitArray or BitStream classes, as only immutable objects should be hashed. You typically won’t need to call it directly, instead it is used for dictionary keys and in sets.

Bits.__invert__()

~s

Returns the bitstring with every bit inverted, that is all zeros replaced with ones, and all ones replaced with zeros.

If the bitstring is empty then an Error will be raised.

>>> s = ConstBitStream(‘0b1110010’)
>>> print(~s)
0b0001101
>>> print(~s & s)
0b0000000
>>> ~~s == s
True
Bits.__len__()

len(s)

Returns the length of the bitstring in bits.

If you are using a 32-bit Python build (which is quite unlikely these days) it’s recommended that you use the len property rather than the len function because of the function will raise a OverflowError if the length is greater than sys.maxsize.

Bits.__lshift__(n)

s << n

Returns the bitstring with its bits shifted n places to the left. The n right-most bits will become zeros.

>>> s = Bits('0xff')
>>> s << 4
Bits('0xf0')
Bits.__mul__(n)
Bits.__rmul__(n)

s * n / n * s

Return bitstring consisting of n concatenations of another.

>>> a = Bits('0x34')
>>> b = a*5
>>> print(b)
0x3434343434
Bits.__ne__(bs)

s1 != s2

Compares two bitstring objects for inequality, returning False if they have the same binary representation, otherwise returning True.

Bits.__nonzero__()

See __bool__.

Bits.__or__(bs)
Bits.__ror__(bs)

s1 | s2

Returns the bit-wise OR between two bitstring, which must have the same length otherwise a ValueError is raised.

>>> print(Bits('0x33') | '0x0f')
0x3f
Bits.__repr__()

repr(s)

A representation of the bitstring that could be used to create it (which will often not be the form used to create it).

If the result is too long then it will be truncated with ... and the length of the whole will be given.

>>> Bits(‘0b11100011’)
Bits(‘0xe3’)
Bits.__rshift__(n)

s >> n

Returns the bitstring with its bits shifted n places to the right. The n left-most bits will become zeros.

>>> s = Bits(‘0xff’)
>>> s >> 4
Bits(‘0x0f’)
Bits.__str__()

print(s)

Used to print a representation of the bitstring, trying to be as brief as possible.

If the bitstring is a multiple of 4 bits long then hex will be used, otherwise either binary or a mix of hex and binary will be used. Very long strings will be truncated with ....

>>> s = Bits('0b1')*7
>>> print(s)
0b1111111
>>> print(s + '0b1')
0xff

See also the pp method for ways to pretty-print the bitstring.

Bits.__xor__(bs)
Bits.__rxor__(bs)

s1 ^ s2

Returns the bit-wise XOR between two bitstrings, which must have the same length otherwise a ValueError is raised.

>>> print(Bits('0x33') ^ '0x0f')
0x3c