class QBitArray

The QBitArray class provides an array of bits. More…

Synopsis

Methods

Static functions

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

A QBitArray is an array that gives access to individual bits and provides operators ( AND , OR , XOR , and NOT ) that work on entire arrays of bits. It uses implicit sharing (copy-on-write) to reduce memory usage and to avoid the needless copying of data.

The following code constructs a QBitArray containing 200 bits initialized to false (0):

ba = QBitArray(200)

To initialize the bits to true, either pass true as second argument to the constructor, or call fill() later on.

QBitArray uses 0-based indexes, just like C++ arrays. To access the bit at a particular index position, you can use operator[](). On non-const bit arrays, operator[]() returns a reference to a bit that can be used on the left side of an assignment. For example:

ba = QBitArray()
ba.resize(3)
ba[0] = True
ba[1] = False
ba[2] = True

For technical reasons, it is more efficient to use testBit() and setBit() to access bits in the array than operator[](). For example:

ba = QBitArray(3)
ba.setBit(0, True)
ba.setBit(1, False)
ba.setBit(2, True)

QBitArray supports & ( AND ), | ( OR ), ^ ( XOR ), ~ ( NOT ), as well as &=, |=, and ^=. These operators work in the same way as the built-in C++ bitwise operators of the same name. For example:

x = QBitArray(5)
x.setBit(3, True)
# x: [ 0, 0, 0, 1, 0 ]
y = QBitArray(5)
y.setBit(4, True)
# y: [ 0, 0, 0, 0, 1 ]
x |= y
# x: [ 0, 0, 0, 1, 1 ]

For historical reasons, QBitArray distinguishes between a null bit array and an empty bit array. A null bit array is a bit array that is initialized using QBitArray ‘s default constructor. An empty bit array is any bit array with size 0. A null bit array is always empty, but an empty bit array isn’t necessarily null:

QBitArray().isNull() # returns true
QBitArray().isEmpty() # returns true
QBitArray(0).isNull() # returns false
QBitArray(0).isEmpty() # returns true
QBitArray(3).isNull() # returns false
QBitArray(3).isEmpty() # returns false

All functions except isNull() treat null bit arrays the same as empty bit arrays; for example, QBitArray() compares equal to QBitArray (0). We recommend that you always use isEmpty() and avoid isNull() .

See also

QByteArray QList

__init__()

Constructs an empty bit array.

See also

isEmpty()

__init__(other)
Parameters:

other – QBitArray

Constructs a copy of other.

This operation takes constant time , because QBitArray is implicitly shared . This makes returning a QBitArray from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes linear time .

See also

operator=()

__init__(size[, val=false])
Parameters:

  • size – int

  • val – bool

Constructs a bit array containing size bits. The bits are initialized with value, which defaults to false (0).

__getitem__()
__len__()
__setitem__()
at(i)
Parameters:

i – int

Return type:

bool

Returns the value of the bit at index position i.

i must be a valid index position in the bit array (i.e., 0 <= i < size() ).

See also

operator[]()

bits()
Return type:

str

Returns a pointer to a dense bit array for this QBitArray . Bits are counted upwards from the least significant bit in each byte. The number of bits relevant in the last byte is given by size() % 8.

See also

fromBits() size()

clear()

Clears the contents of the bit array and makes it empty.

See also

resize() isEmpty()

clearBit(i)
Parameters:

i – int

Sets the bit at index position i to 0.

i must be a valid index position in the bit array (i.e., 0 <= i < size() ).

count()
Return type:

int

Same as size() .

count(on)
Parameters:

on – bool

Return type:

int

If on is true, this function returns the number of 1-bits stored in the bit array; otherwise the number of 0-bits is returned.

fill(aval[, asize=-1])
Parameters:

  • aval – bool

  • asize – int

Return type:

bool

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Sets every bit in the bit array to value, returning true if successful; otherwise returns false. If size is different from -1 (the default), the bit array is resized to size beforehand.

Example:

ba = QBitArray(8)
ba.fill(True)
# ba: [ 1, 1, 1, 1, 1, 1, 1, 1 ]
ba.fill(False, 2)
# ba: [ 0, 0 ]

See also

resize()

fill(val, first, last)
Parameters:

  • val – bool

  • first – int

  • last – int

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

This is an overloaded function.

Sets bits at index positions begin up to (but not including) end to value.

begin must be a valid index position in the bit array (0 <= begin < size() ).

end must be either a valid index position or equal to size() , in which case the fill operation runs until the end of the array (0 <= end <= size() ).

Example:

ba = QBitArray(4)
ba.fill(True, 1, 2) # ba: [ 0, 1, 0, 0 ]
ba.fill(True, 1, 3) # ba: [ 0, 1, 1, 0 ]
ba.fill(True, 1, 4) # ba: [ 0, 1, 1, 1 ]
static fromBits(data, len)
Parameters:

  • data – str

  • len – int

Return type:

QBitArray

Creates a QBitArray with the dense bit array located at data, with size bits. The byte array at data must be at least size / 8 (rounded up) bytes long.

If size is not a multiple of 8, this function will include the lowest size % 8 bits from the last byte in data.

See also

bits()

isEmpty()
Return type:

bool

Returns true if this bit array has size 0; otherwise returns false.

See also

size()

isNull()
Return type:

bool

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Returns true if this bit array is null; otherwise returns false.

Example:

QBitArray().isNull() # returns true
QBitArray(0).isNull() # returns false
QBitArray(3).isNull() # returns false

Qt makes a distinction between null bit arrays and empty bit arrays for historical reasons. For most applications, what matters is whether or not a bit array contains any data, and this can be determined using isEmpty() .

See also

isEmpty()

__ne__(rhs)
Parameters:

rhs – QBitArray

Return type:

bool

Returns true if lhs is not equal to rhs bit array; otherwise returns false.

See also

operator==()

__and__(a2)
Parameters:

a2 – QBitArray

Return type:

QBitArray

__iand__(arg__1)
Parameters:

arg__1 – QBitArray

Return type:

QBitArray

__eq__(rhs)
Parameters:

rhs – QBitArray

Return type:

bool

Returns true if lhs is equal to rhs bit array; otherwise returns false.

See also

operator!=()

operator(i)
Parameters:

i – int

Return type:

bool

This is an overloaded function.

__xor__(a2)
Parameters:

a2 – QBitArray

Return type:

QBitArray

__ixor__(arg__1)
Parameters:

arg__1 – QBitArray

Return type:

QBitArray

__or__(a2)
Parameters:

a2 – QBitArray

Return type:

QBitArray

__ior__(arg__1)
Parameters:

arg__1 – QBitArray

Return type:

QBitArray

__invert__()
Return type:

QBitArray

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Returns a bit array that contains the inverted bits of the bit array a.

Example:

a = QBitArray(3)
b = QBitArray()
a[0] = 1 a[1] = 0; a[2] = 1; # a: [ 1, 0, 1 ]
b = ~a # b: [ 0, 1, 0 ]

See also

operator&() operator|() operator^()

resize(size)
Parameters:

size – int

Resizes the bit array to size bits.

If size is greater than the current size, the bit array is extended to make it size bits with the extra bits added to the end. The new bits are initialized to false (0).

If size is less than the current size, bits are removed from the end.

See also

size()

setBit(i)
Parameters:

i – int

Sets the bit at index position i to 1.

i must be a valid index position in the bit array (i.e., 0 <= i < size() ).

setBit(i, val)
Parameters:

  • i – int

  • val – bool

This is an overloaded function.

Sets the bit at index position i to value.

size()
Return type:

int

Returns the number of bits stored in the bit array.

See also

resize()

swap(other)
Parameters:

other – QBitArray

Swaps bit array other with this bit array. This operation is very fast and never fails.

testBit(i)
Parameters:

i – int

Return type:

bool

Returns true if the bit at index position i is 1; otherwise returns false.

i must be a valid index position in the bit array (i.e., 0 <= i < size() ).

See also

setBit() clearBit()

toUInt32(endianness[, ok=None])
Parameters:

  • endianness – Endian

  • ok – bool

Return type:

int

Returns the array of bit converted to an int. The conversion is based on endianness. Converts up to the first 32 bits of the array to quint32 and returns it, obeying endianness. If ok is not a null pointer, and the array has more than 32 bits, ok is set to false and this function returns zero; otherwise, it’s set to true.

toggleBit(i)
Parameters:

i – int

Return type:

bool

Inverts the value of the bit at index position i, returning the previous value of that bit as either true (if it was set) or false (if it was unset).

If the previous value was 0, the new value will be 1. If the previous value was 1, the new value will be 0.

i must be a valid index position in the bit array (i.e., 0 <= i < size() ).

See also

setBit() clearBit()

truncate(pos)
Parameters:

pos – int

Truncates the bit array at index position pos.

If pos is beyond the end of the array, nothing happens.

See also

resize()