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A pure-Python memory-efficient packed representation for bit arrays

Project description

This class presents a pure-Python memory efficient packed representation for bit arrays.

Fixed a potentially misleading documentation issue for the Windows users of the BitVector class. If you are writing an internally generated BitVector to a disk file, you must open the file in the binary mode. If you don’t, the bit patterns that correspond to line breaks will be misinterpreted. On a Windows machine in the text mode, the bit pattern 000001010 (‘\n’) will be written out to the disk as 0000110100001010 (‘\r\n’).

Change introduced in version 1.3.1: Removed the inconsistency in the internal representation of bit vectors produced by logical bitwise operations vis-a-vis the bit vectors created by the constructor. Previously, the logical bitwise operations resulted in bit vectors that had their bits packed into lists of ints, as opposed to arrays of unsigned shorts.

Changes introduced in version 1.3: (1) One more constructor mode included: When initializing a new bit vector with an integer value, you can now also specify a size for the bit vector. The constructor zero-pads the bit vector from the left with zeros. (2) The BitVector class now supports ‘if x in y’ syntax to test if the bit pattern ‘x’ is contained in the bit pattern ‘y’. (3) Improved syntax to conform to well-established Python idioms. (4) What used to be a comment before the beginning of each method definition is now a docstring.

The class supports the following operators/methods:

__getitem__

__setitem__

__len__

__getslice__

__str__

__iter__

__contains__

__int__

__add__

__eq__, __ne__, __lt__, __le__, __gt__, __ge__

‘|’ for bitwise or

‘&’ for bitwise and

‘^’ for bitwise xor

‘~’ for bitwise inversion

‘<<’ for circular shift to the left

‘>>’ for circular shift to the right

‘+’ for concatenation

intValue(), __int__ for returning the integer value

divide_into_two

permute

unpermute

pad_from_left

pad_from_right

read_bits_from_file

write_to_file

read_bits_from_fileobject

write_bits_to_fileobject

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