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 argumentsbytes
,bin
,hex
,oct
,uint
,int
,uintbe
,intbe
,uintle
,intle
,uintne
,intne
,se
,ue
,sie
,uie
,float
,floatbe
,floatle
,floatne
,bool
orfilename
. If no initialiser is given then a zeroed bitstring oflength
bits is created.The initialiser for the
Bits
class is precisely the same as forBitArray
,BitStream
andConstBitStream
.offset
is available when using thebytes
orfilename
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 inlength
bits. It must also be specified for the float initialisers (the only valid values are 32 and 64). It is optional for thebytes
andfilename
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 returnsFalse
.If value is
True
then1
bits are checked for, otherwise0
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
ifpos < s.len
orpos > 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 returnsFalse
.If value is
True
then1
bits are checked for, otherwise0
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
ifpos < s.len
orpos > 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
orFalse
or anything that can be cast to a bool, so you could equally use1
or0
.>>> 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 substring bs, otherwise returnsFalse
.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 to0
andlen
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 substring bs, otherwise returnsFalse
.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 astr
in Python 2.6/2.7).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
orFalse
).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 seven0
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 bytewise bigendian signed two’s complement integer representation of the bitstring.
Only valid for wholebyte bitstrings, in which case it is equal to
s.int
, otherwise anInterpretError
is raised.

intle
¶ Property for the bytewise littleendian signed two’s complement integer representation of the bitstring.
Only valid for wholebyte bitstring, in which case it is equal to
s[::8].int
, i.e. the integer representation of the bytereversed bitstring.

intne
¶ Property for the bytewise nativeendian signed two’s complement integer representation of the bitstring.
Only valid for wholebyte bitstrings, and will equal either the bigendian or the littleendian 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 bitwise bigendian, which as all floats must be wholebyte is exactly equivalent to the bytewise bigendianfloatbe
.

floatle
¶ Property for the bytewise littleendian floating point representation of the bitstring.

floatne
¶ Property for the bytewise nativeendian floating point representation of the bitstring.

len
¶

length
¶ Readonly property that give the length of the bitstring in bits (
len
andlength
are equivalent).This is almost equivalent to using the
len()
builtin function, except that for large bitstringslen()
may fail with anOverflowError
, whereas thelen
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 exponentialGolomb 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 exponentialGolomb code.

ue
¶ Property for the unsigned exponentialGolomb 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 exponentialGolomb 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 exponentialGolomb 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 base2 integer representation of the bitstring.

uintbe
¶ Property for the bytewise bigendian unsigned base2 integer representation of the bitstring.

uintle
¶ Property for the bytewise littleendian unsigned base2 integer representation of the bitstring.

uintne
¶ Property for the bytewise nativeendian unsigned base2 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 bitwise 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 returnsFalse
.This special method is used in Python 3 only; for Python 2 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 returnsFalse
.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 returningFalse
.>>> 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
orFalse
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
orBitStream
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 raisesOverflowError
.It’s recommended that you use the
len
property rather than thelen
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 rightmost 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 returningTrue
.

__or__
(bs)¶

__ror__
(bs)¶ s1  s2
Returns the bitwise 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 leftmost 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 bitwise XOR between two bitstrings, which must have the same length otherwise a
ValueError
is raised.>>> print(Bits('0x33') ^ '0x0f') 0x3c
