The Bits class

class bitstring.Bits([auto, length, offset, **kwargs])

Creates a new bitstring. You must specify either no initialiser, just an auto value, or one of the keyword arguments bytes, bin, hex, oct, uint, int, uintbe, intbe, uintle, intle, uintne, intne, se, ue, sie, uie, float, floatbe, floatle, floatne, bool or filename. 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 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

For information on the use of auto see The auto initialiser.

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

all(value[, pos])

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 < -s.len or pos > s.len. It defaults to the whole bitstring.

>>> s = Bits('int:15=-1')
>>> s.all(True, [3, 4, 12, 13])
True
>>> s.all(1)
True

any(value[, pos])

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 < -s.len or pos > s.len. It defaults to the whole bitstring.

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

count(value)

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

cut(bits[, start, end, count])

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 = BitString('0x1234')
>>> for nibble in s.cut(4):
...     s.prepend(nibble)
>>> print(s)
0x43211234

endswith(bs[, start, end])

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

find(bs[, start, end, bytealigned])

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,)

findall(bs[, start, end, count, bytealigned])

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 paramater limits the number of items that will be found - the default is to find all occurences.

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

join(sequence)

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

rfind(bs[, start, end, bytealigned])

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,)

split(delimiter[, start, end, count, bytealigned])

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']

startswith(bs[, start, end])

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.

tobytes()

Returns the bitstring as a bytes object (equivalent to a str in Python 2.7).

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

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@'

tofile(f)

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)

unpack(fmt, **kwargs)

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 entry for read for details.

>>> s = Bits('int:4=-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.

bin

Property for the representation of the bitstring as a binary string.

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.

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'

hex

Property representing the hexadecimal value of the bitstring.

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'

int

Property for the signed two’s complement integer representation of the bitstring.

intbe

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.

intle

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.

intne

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.

float

floatbe

Property for the floating point representation of the bitstring.

The bitstring must be either 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.

floatle

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

floatne

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

len

length

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

This is almost equivalent to using the len() built-in function, except that for large bitstrings len() may fail with an OverflowError, whereas the len property continues to work.

oct

Property for the octal representation of the bitstring.

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

>>> s = BitString('0b111101101')
>>> s.oct
'755'
>>> s.oct = '01234567'
>>> s.oct
'01234567'

se

Property for the signed exponential-Golomb code representation of the bitstring.

When used as a getter an InterpretError will be raised if the bitstring is not a single code.

>>> s = BitString(se=-40)
>>> s.bin
0000001010001
>>> s += '0b1'
>>> s.se
Error: BitString is not a single exponential-Golomb code.

ue

Property for the unsigned exponential-Golomb code representation of the bitstring.

When used as a getter an InterpretError will be raised if the bitstring is not a single code.

sie

Property for the signed interleaved exponential-Golomb code representation of the bitstring.

When used as a getter an InterpretError will be raised if the bitstring is not a single code.

uie

Property for the unsigned interleaved exponential-Golomb code representation of the bitstring.

When used as a getter an InterpretError will be raised if the bitstring is not a single code.

uint

Property for the unsigned base-2 integer representation of the bitstring.

uintbe

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

uintle

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

uintne

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

__add__(bs)

__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

__and__(bs)

__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

__bool__()

if s:

Returns True if at least one bit is set to 1, otherwise returns False.

This special method is used in Python 3 only; for Python 2.7 the equivalent is called __nonzero__, but the details are exactly the same.

>>> bool(Bits())
False
>>> bool(Bits('0b0000010000'))
True
>>> bool(Bits('0b0000000000'))
False

__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

__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

__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

__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

__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.

__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

__len__()

len(s)

Returns the length of the bitstring in bits if it is less than sys.maxsize, otherwise raises OverflowError.

It’s recommended that you use the len property rather than the len function because of the function’s behaviour for large bitstring objects, although calling the special function directly will always work.

>>> s = Bits(filename='11GB.mkv')
>>> s.len
93944160032
>>> len(s)
OverflowError: long int too large to convert to int
>>> s.__len__()
93944160032

__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')

__mul__(n)

__rmul__(n)

s * n / n * s

Return bitstring consisting of n concatenations of another.

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

__ne__(bs)

s1 != s2

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

__nonzero__()

See __bool__.

__or__(bs)

__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

__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’)

__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’)

__str__()

print(s)

Used to print a representation of 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

__xor__(bs)

__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